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Diffstat (limited to 'mysys/mf_keycache.c')
| -rw-r--r-- | mysys/mf_keycache.c | 6577 |
1 files changed, 6577 insertions, 0 deletions
diff --git a/mysys/mf_keycache.c b/mysys/mf_keycache.c new file mode 100644 index 00000000..4b0fef18 --- /dev/null +++ b/mysys/mf_keycache.c @@ -0,0 +1,6577 @@ +/* Copyright (c) 2000, 2013, Oracle and/or its affiliates. + Copyright (c) 2017, 2022, MariaDB Corporation. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; version 2 of the License. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software + Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */ + + + +/** + @file + The file contains the following modules: + + Simple Key Cache Module + + Partitioned Key Cache Module + + Key Cache Interface Module + +*/ + +#include "mysys_priv.h" +#include "mysys_err.h" +#include <keycache.h> +#include "my_static.h" +#include <m_string.h> +#include <my_bit.h> +#include <errno.h> +#include <stdarg.h> +#include "probes_mysql.h" + +/****************************************************************************** + Simple Key Cache Module + + The module contains implementations of all key cache interface functions + employed by partitioned key caches. + +******************************************************************************/ + +/* + These functions handle keyblock cacheing for ISAM and MyISAM tables. + + One cache can handle many files. + It must contain buffers of the same blocksize. + + init_key_cache() should be used to init cache handler. + + The free list (free_block_list) is a stack like structure. + When a block is freed by free_block(), it is pushed onto the stack. + When a new block is required it is first tried to pop one from the stack. + If the stack is empty, it is tried to get a never-used block from the pool. + If this is empty too, then a block is taken from the LRU ring, flushing it + to disk, if necessary. This is handled in find_key_block(). + With the new free list, the blocks can have three temperatures: + hot, warm and cold (which is free). This is remembered in the block header + by the enum BLOCK_TEMPERATURE temperature variable. Remembering the + temperature is necessary to correctly count the number of warm blocks, + which is required to decide when blocks are allowed to become hot. Whenever + a block is inserted to another (sub-)chain, we take the old and new + temperature into account to decide if we got one more or less warm block. + blocks_unused is the sum of never used blocks in the pool and of currently + free blocks. blocks_used is the number of blocks fetched from the pool and + as such gives the maximum number of in-use blocks at any time. + + Key Cache Locking + ================= + + All key cache locking is done with a single mutex per key cache: + keycache->cache_lock. This mutex is locked almost all the time + when executing code in this file (mf_keycache.c). + However it is released for I/O and some copy operations. + + The cache_lock is also released when waiting for some event. Waiting + and signalling is done via condition variables. In most cases the + thread waits on its thread->suspend condition variable. Every thread + has a my_thread_var structure, which contains this variable and a + '*next' and '**prev' pointer. These pointers are used to insert the + thread into a wait queue. + + A thread can wait for one block and thus be in one wait queue at a + time only. + + Before starting to wait on its condition variable with + mysql_cond_wait(), the thread enters itself to a specific wait queue + with link_into_queue() (double linked with '*next' + '**prev') or + wait_on_queue() (single linked with '*next'). + + Another thread, when releasing a resource, looks up the waiting thread + in the related wait queue. It sends a signal with + mysql_cond_signal() to the waiting thread. + + NOTE: Depending on the particular wait situation, either the sending + thread removes the waiting thread from the wait queue with + unlink_from_queue() or release_whole_queue() respectively, or the waiting + thread removes itself. + + There is one exception from this locking scheme when one thread wants + to reuse a block for some other address. This works by first marking + the block reserved (status= BLOCK_IN_SWITCH) and then waiting for all + threads that are reading the block to finish. Each block has a + reference to a condition variable (condvar). It holds a reference to + the thread->suspend condition variable for the waiting thread (if such + a thread exists). When that thread is signaled, the reference is + cleared. The number of readers of a block is registered in + block->hash_link->requests. See wait_for_readers() / remove_reader() + for details. This is similar to the above, but it clearly means that + only one thread can wait for a particular block. There is no queue in + this case. Strangely enough block->convar is used for waiting for the + assigned hash_link only. More precisely it is used to wait for all + requests to be unregistered from the assigned hash_link. + + The resize_queue serves two purposes: + 1. Threads that want to do a resize wait there if in_resize is set. + This is not used in the server. The server refuses a second resize + request if one is already active. keycache->in_init is used for the + synchronization. See set_var.cc. + 2. Threads that want to access blocks during resize wait here during + the re-initialization phase. + When the resize is done, all threads on the queue are signalled. + Hypothetical resizers can compete for resizing, and read/write + requests will restart to request blocks from the freshly resized + cache. If the cache has been resized too small, it is disabled and + 'can_be_used' is false. In this case read/write requests bypass the + cache. Since they increment and decrement 'cnt_for_resize_op', the + next resizer can wait on the queue 'waiting_for_resize_cnt' until all + I/O finished. +*/ + +/* declare structures that is used by st_key_cache */ + +struct st_block_link; +typedef struct st_block_link BLOCK_LINK; +struct st_keycache_page; +typedef struct st_keycache_page KEYCACHE_PAGE; +struct st_hash_link; +typedef struct st_hash_link HASH_LINK; + +/* info about requests in a waiting queue */ +typedef struct st_keycache_wqueue +{ + struct st_my_thread_var *last_thread; /* circular list of waiting threads */ +} KEYCACHE_WQUEUE; + +/* Default size of hash for changed files */ +#define MIN_CHANGED_BLOCKS_HASH_SIZE 128 + +/* Control block for a simple (non-partitioned) key cache */ + +typedef struct st_simple_key_cache_cb +{ + my_bool key_cache_inited; /* <=> control block is allocated */ + my_bool in_resize; /* true during resize operation */ + my_bool resize_in_flush; /* true during flush of resize operation */ + my_bool can_be_used; /* usage of cache for read/write is allowed */ + size_t key_cache_mem_size; /* specified size of the cache memory */ + size_t allocated_mem_size; /* size of the memory actually allocated */ + uint key_cache_block_size; /* size of the page buffer of a cache block */ + size_t min_warm_blocks; /* min number of warm blocks; */ + size_t age_threshold; /* age threshold for hot blocks */ + ulonglong keycache_time; /* total number of block link operations */ + uint hash_entries; /* max number of entries in the hash table */ + uint changed_blocks_hash_size; /* Number of hash buckets for file blocks */ + int hash_links; /* max number of hash links */ + int hash_links_used; /* number of hash links currently used */ + int disk_blocks; /* max number of blocks in the cache */ + size_t blocks_used; /* maximum number of concurrently used blocks */ + size_t blocks_unused; /* number of currently unused blocks */ + size_t blocks_changed; /* number of currently dirty blocks */ + size_t warm_blocks; /* number of blocks in warm sub-chain */ + ulong cnt_for_resize_op; /* counter to block resize operation */ + long blocks_available; /* number of blocks available in the LRU chain */ + HASH_LINK **hash_root; /* arr. of entries into hash table buckets */ + HASH_LINK *hash_link_root; /* memory for hash table links */ + HASH_LINK *free_hash_list; /* list of free hash links */ + BLOCK_LINK *free_block_list; /* list of free blocks */ + BLOCK_LINK *block_root; /* memory for block links */ + uchar *block_mem; /* memory for block buffers */ + BLOCK_LINK *used_last; /* ptr to the last block of the LRU chain */ + BLOCK_LINK *used_ins; /* ptr to the insertion block in LRU chain */ + mysql_mutex_t cache_lock; /* to lock access to the cache structure */ + KEYCACHE_WQUEUE resize_queue; /* threads waiting during resize operation */ + /* + Waiting for a zero resize count. Using a queue for symmetry though + only one thread can wait here. + */ + KEYCACHE_WQUEUE waiting_for_resize_cnt; + KEYCACHE_WQUEUE waiting_for_hash_link; /* waiting for a free hash link */ + KEYCACHE_WQUEUE waiting_for_block; /* requests waiting for a free block */ + BLOCK_LINK **changed_blocks; /* hash for dirty file bl.*/ + BLOCK_LINK **file_blocks; /* hash for other file bl.*/ + + /* Statistics variables. These are reset in reset_key_cache_counters(). */ + ulong global_blocks_changed; /* number of currently dirty blocks */ + ulonglong global_cache_w_requests;/* number of write requests (write hits) */ + ulonglong global_cache_write; /* number of writes from cache to files */ + ulonglong global_cache_r_requests;/* number of read requests (read hits) */ + ulonglong global_cache_read; /* number of reads from files to cache */ + + int blocks; /* max number of blocks in the cache */ + uint hash_factor; /* factor used to calculate hash function */ + my_bool in_init; /* Set to 1 in MySQL during init/resize */ +} SIMPLE_KEY_CACHE_CB; + +/* + Some compilation flags have been added specifically for this module + to control the following: + - not to let a thread to yield the control when reading directly + from key cache, which might improve performance in many cases; + to enable this add: + #define SERIALIZED_READ_FROM_CACHE + - to set an upper bound for number of threads simultaneously + using the key cache; this setting helps to determine an optimal + size for hash table and improve performance when the number of + blocks in the key cache much less than the number of threads + accessing it; + to set this number equal to <N> add + #define MAX_THREADS <N> + - to substitute calls of mysql_cond_wait for calls of + mysql_cond_timedwait (wait with timeout set up); + this setting should be used only when you want to trap a deadlock + situation, which theoretically should not happen; + to set timeout equal to <T> seconds add + #define KEYCACHE_TIMEOUT <T> + - to enable the module traps and to send debug information from + key cache module to a special debug log add: + #define KEYCACHE_DEBUG + the name of this debug log file <LOG NAME> can be set through: + #define KEYCACHE_DEBUG_LOG <LOG NAME> + if the name is not defined, it's set by default; + if the KEYCACHE_DEBUG flag is not set up and we are in a debug + mode, i.e. when ! defined(DBUG_OFF), the debug information from the + module is sent to the regular debug log. + + Example of the settings: + #define SERIALIZED_READ_FROM_CACHE + #define MAX_THREADS 100 + #define KEYCACHE_TIMEOUT 1 + #define KEYCACHE_DEBUG + #define KEYCACHE_DEBUG_LOG "my_key_cache_debug.log" +*/ + +#define STRUCT_PTR(TYPE, MEMBER, a) \ + (TYPE *) ((char *) (a) - offsetof(TYPE, MEMBER)) + +/* types of condition variables */ +#define COND_FOR_REQUESTED 0 +#define COND_FOR_SAVED 1 +#define COND_FOR_READERS 2 + +typedef mysql_cond_t KEYCACHE_CONDVAR; + +/* descriptor of the page in the key cache block buffer */ +struct st_keycache_page +{ + int file; /* file to which the page belongs to */ + my_off_t filepos; /* position of the page in the file */ +}; + +/* element in the chain of a hash table bucket */ +struct st_hash_link +{ + struct st_hash_link *next, **prev; /* to connect links in the same bucket */ + struct st_block_link *block; /* reference to the block for the page: */ + File file; /* from such a file */ + my_off_t diskpos; /* with such an offset */ + uint requests; /* number of requests for the page */ +}; + +/* simple states of a block */ +#define BLOCK_ERROR 1U/* an error occurred when performing file i/o */ +#define BLOCK_READ 2U/* file block is in the block buffer */ +#define BLOCK_IN_SWITCH 4U/* block is preparing to read new page */ +#define BLOCK_REASSIGNED 8U/* blk does not accept requests for old page */ +#define BLOCK_IN_FLUSH 16U/* block is selected for flush */ +#define BLOCK_CHANGED 32U/* block buffer contains a dirty page */ +#define BLOCK_IN_USE 64U/* block is not free */ +#define BLOCK_IN_EVICTION 128U/* block is selected for eviction */ +#define BLOCK_IN_FLUSHWRITE 256U/* block is in write to file */ +#define BLOCK_FOR_UPDATE 512U/* block is selected for buffer modification */ + +/* page status, returned by find_key_block */ +#define PAGE_READ 0 +#define PAGE_TO_BE_READ 1 +#define PAGE_WAIT_TO_BE_READ 2 + +/* block temperature determines in which (sub-)chain the block currently is */ +enum BLOCK_TEMPERATURE { BLOCK_COLD /*free*/ , BLOCK_WARM , BLOCK_HOT }; + +/* key cache block */ +struct st_block_link +{ + struct st_block_link + *next_used, **prev_used; /* to connect links in the LRU chain (ring) */ + struct st_block_link + *next_changed, **prev_changed; /* for lists of file dirty/clean blocks */ + struct st_hash_link *hash_link; /* backward ptr to referring hash_link */ + KEYCACHE_WQUEUE wqueue[2]; /* queues on waiting requests for new/old pages */ + uint requests; /* number of requests for the block */ + uchar *buffer; /* buffer for the block page */ + uint offset; /* beginning of modified data in the buffer */ + uint length; /* end of data in the buffer */ + uint status; /* state of the block */ + enum BLOCK_TEMPERATURE temperature; /* block temperature: cold, warm, hot */ + uint hits_left; /* number of hits left until promotion */ + ulonglong last_hit_time; /* timestamp of the last hit */ + KEYCACHE_CONDVAR *condvar; /* condition variable for 'no readers' event */ +}; + +KEY_CACHE dflt_key_cache_var; +KEY_CACHE *dflt_key_cache= &dflt_key_cache_var; + +#define FLUSH_CACHE 2000 /* sort this many blocks at once */ + +static int flush_all_key_blocks(SIMPLE_KEY_CACHE_CB *keycache); +static void end_simple_key_cache(SIMPLE_KEY_CACHE_CB *keycache, my_bool cleanup); +static void wait_on_queue(KEYCACHE_WQUEUE *wqueue, + mysql_mutex_t *mutex); +static void release_whole_queue(KEYCACHE_WQUEUE *wqueue); +static void free_block(SIMPLE_KEY_CACHE_CB *keycache, BLOCK_LINK *block); +#ifndef DBUG_OFF +static void test_key_cache(SIMPLE_KEY_CACHE_CB *keycache, + const char *where, my_bool lock); +#endif +#define KEYCACHE_BASE_EXPR(f, pos) \ + ((ulong) ((pos) / keycache->key_cache_block_size) + (ulong) (f)) +#define KEYCACHE_HASH(f, pos) \ + ((KEYCACHE_BASE_EXPR(f, pos) / keycache->hash_factor) & \ + (keycache->hash_entries-1)) +#define FILE_HASH(f, cache) ((uint) (f) & (cache->changed_blocks_hash_size-1)) + +#define DEFAULT_KEYCACHE_DEBUG_LOG "keycache_debug.log" + +#if defined(KEYCACHE_DEBUG) && ! defined(KEYCACHE_DEBUG_LOG) +#define KEYCACHE_DEBUG_LOG DEFAULT_KEYCACHE_DEBUG_LOG +#endif + +#if defined(KEYCACHE_DEBUG_LOG) +static FILE *keycache_debug_log=NULL; +static void keycache_debug_print(const char *fmt,...); +#define KEYCACHE_DEBUG_OPEN \ + if (!keycache_debug_log) \ + { \ + keycache_debug_log= fopen(KEYCACHE_DEBUG_LOG, "w"); \ + (void) setvbuf(keycache_debug_log, NULL, _IOLBF, BUFSIZ); \ + } + +#define KEYCACHE_DEBUG_CLOSE \ + if (keycache_debug_log) \ + { \ + fclose(keycache_debug_log); \ + keycache_debug_log= 0; \ + } +#else +#define KEYCACHE_DEBUG_OPEN +#define KEYCACHE_DEBUG_CLOSE +#endif /* defined(KEYCACHE_DEBUG_LOG) */ + +#if defined(KEYCACHE_DEBUG_LOG) && defined(KEYCACHE_DEBUG) +#define KEYCACHE_DBUG_PRINT(l, m) \ + { if (keycache_debug_log) fprintf(keycache_debug_log, "%s: ", l); \ + keycache_debug_print m; } + +#define KEYCACHE_DBUG_ASSERT(a) \ + { if (! (a) && keycache_debug_log) fclose(keycache_debug_log); \ + assert(a); } +#else +#define KEYCACHE_DBUG_PRINT(l, m) DBUG_PRINT(l, m) +#define KEYCACHE_DBUG_ASSERT(a) DBUG_ASSERT(a) +#endif /* defined(KEYCACHE_DEBUG_LOG) && defined(KEYCACHE_DEBUG) */ + +#if defined(KEYCACHE_DEBUG) || defined(DBUG_TRACE) +static long keycache_thread_id; +#define KEYCACHE_THREAD_TRACE(l) \ + KEYCACHE_DBUG_PRINT(l,("|thread %ld",keycache_thread_id)) + +#define KEYCACHE_THREAD_TRACE_BEGIN(l) \ + { struct st_my_thread_var *thread_var= my_thread_var; \ + keycache_thread_id= thread_var->id; \ + KEYCACHE_DBUG_PRINT(l,("[thread %ld",keycache_thread_id)) } + +#define KEYCACHE_THREAD_TRACE_END(l) \ + KEYCACHE_DBUG_PRINT(l,("]thread %ld",keycache_thread_id)) +#else +#define KEYCACHE_THREAD_TRACE_BEGIN(l) +#define KEYCACHE_THREAD_TRACE_END(l) +#define KEYCACHE_THREAD_TRACE(l) +#endif /* defined(KEYCACHE_DEBUG) || defined(DBUG_TRACE) */ + +#define BLOCK_NUMBER(b) \ + ((uint) (((char*)(b)-(char *) keycache->block_root)/sizeof(BLOCK_LINK))) +#define HASH_LINK_NUMBER(h) \ + ((uint) (((char*)(h)-(char *) keycache->hash_link_root)/sizeof(HASH_LINK))) + +#if (defined(KEYCACHE_TIMEOUT) && !defined(_WIN32)) || defined(KEYCACHE_DEBUG) +static int keycache_pthread_cond_wait(mysql_cond_t *cond, + mysql_mutex_t *mutex); +#else +#define keycache_pthread_cond_wait(C, M) mysql_cond_wait(C, M) +#endif + +#if defined(KEYCACHE_DEBUG) +static int keycache_pthread_mutex_lock(mysql_mutex_t *mutex); +static void keycache_pthread_mutex_unlock(mysql_mutex_t *mutex); +static int keycache_pthread_cond_signal(mysql_cond_t *cond); +#else +#define keycache_pthread_mutex_lock(M) mysql_mutex_lock(M) +#define keycache_pthread_mutex_unlock(M) mysql_mutex_unlock(M) +#define keycache_pthread_cond_signal(C) mysql_cond_signal(C) +#endif /* defined(KEYCACHE_DEBUG) */ + +#if !defined(DBUG_OFF) +#if defined(inline) +#undef inline +#endif +#define inline /* disabled inline for easier debugging */ +static int fail_hlink(HASH_LINK *hlink); +static int cache_empty(SIMPLE_KEY_CACHE_CB *keycache); +#endif +#ifdef DBUG_ASSERT_EXISTS +static int fail_block(BLOCK_LINK *block); +#endif + +static inline uint next_power(uint value) +{ + return (uint) my_round_up_to_next_power((uint32) value) << 1; +} + + +/* + Initialize a simple key cache + + SYNOPSIS + init_simple_key_cache() + keycache pointer to the control block of a simple key cache + key_cache_block_size size of blocks to keep cached data + use_mem memory to use for the key cache buferrs/structures + division_limit division limit (may be zero) + age_threshold age threshold (may be zero) + + DESCRIPTION + This function is the implementation of the init_key_cache interface + function that is employed by simple (non-partitioned) key caches. + The function builds a simple key cache and initializes the control block + structure of the type SIMPLE_KEY_CACHE_CB that is used for this key cache. + The parameter keycache is supposed to point to this structure. + The parameter key_cache_block_size specifies the size of the blocks in + the key cache to be built. The parameters division_limit and age_threshold + determine the initial values of those characteristics of the key cache + that are used for midpoint insertion strategy. The parameter use_mem + specifies the total amount of memory to be allocated for key cache blocks + and auxiliary structures. + + RETURN VALUE + number of blocks in the key cache, if successful, + <= 0 - otherwise. + + NOTES. + if keycache->key_cache_inited != 0 we assume that the key cache + is already initialized. This is for now used by myisamchk, but shouldn't + be something that a program should rely on! + + It's assumed that no two threads call this function simultaneously + referring to the same key cache handle. +*/ + +static +int init_simple_key_cache(SIMPLE_KEY_CACHE_CB *keycache, + uint key_cache_block_size, + size_t use_mem, uint division_limit, + uint age_threshold, uint changed_blocks_hash_size) +{ + size_t blocks, hash_links; + size_t length; + int error; + DBUG_ENTER("init_simple_key_cache"); + DBUG_ASSERT(key_cache_block_size >= 512); + + KEYCACHE_DEBUG_OPEN; + if (keycache->key_cache_inited && keycache->disk_blocks > 0) + { + DBUG_PRINT("warning",("key cache already in use")); + DBUG_RETURN(0); + } + + keycache->blocks_used= keycache->blocks_unused= 0; + keycache->global_blocks_changed= 0; + keycache->global_cache_w_requests= keycache->global_cache_r_requests= 0; + keycache->global_cache_read= keycache->global_cache_write= 0; + keycache->disk_blocks= -1; + if (! keycache->key_cache_inited) + { + keycache->key_cache_inited= 1; + keycache->hash_factor= 1; + /* + Initialize these variables once only. + Their value must survive re-initialization during resizing. + */ + keycache->in_resize= 0; + keycache->resize_in_flush= 0; + keycache->cnt_for_resize_op= 0; + keycache->waiting_for_resize_cnt.last_thread= NULL; + keycache->in_init= 0; + mysql_mutex_init(key_KEY_CACHE_cache_lock, + &keycache->cache_lock, MY_MUTEX_INIT_FAST); + keycache->resize_queue.last_thread= NULL; + } + + keycache->key_cache_mem_size= use_mem; + keycache->key_cache_block_size= key_cache_block_size; + DBUG_PRINT("info", ("key_cache_block_size: %u", + key_cache_block_size)); + + blocks= use_mem / (sizeof(BLOCK_LINK) + 2 * sizeof(HASH_LINK) + + sizeof(HASH_LINK*) * 5/4 + key_cache_block_size); + + /* Changed blocks hash needs to be a power of 2 */ + changed_blocks_hash_size= my_round_up_to_next_power(MY_MAX(changed_blocks_hash_size, + MIN_CHANGED_BLOCKS_HASH_SIZE)); + + /* It doesn't make sense to have too few blocks (less than 8) */ + if (blocks >= 8) + { + for ( ; ; ) + { + /* Set my_hash_entries to the next bigger 2 power */ + if ((keycache->hash_entries= next_power((uint)blocks)) < blocks * 5/4) + keycache->hash_entries<<= 1; + hash_links= 2 * blocks; +#if defined(MAX_THREADS) + if (hash_links < MAX_THREADS + blocks - 1) + hash_links= MAX_THREADS + blocks - 1; +#endif + while ((length= (ALIGN_SIZE(blocks * sizeof(BLOCK_LINK)) + + ALIGN_SIZE(hash_links * sizeof(HASH_LINK)) + + ALIGN_SIZE(sizeof(HASH_LINK*) * + keycache->hash_entries) + + sizeof(BLOCK_LINK*)* ((size_t)changed_blocks_hash_size*2))) + + (blocks * keycache->key_cache_block_size) > use_mem && blocks > 8) + blocks--; + keycache->allocated_mem_size= blocks * keycache->key_cache_block_size; + if ((keycache->block_mem= my_large_malloc(&keycache->allocated_mem_size, + MYF(0)))) + { + /* + Allocate memory for blocks, hash_links and hash entries; + For each block 2 hash links are allocated + */ + if (my_multi_malloc_large(key_memory_KEY_CACHE, MYF(MY_ZEROFILL), + &keycache->block_root, + (ulonglong) (blocks * sizeof(BLOCK_LINK)), + &keycache->hash_root, + (ulonglong) (sizeof(HASH_LINK*) * + keycache->hash_entries), + &keycache->hash_link_root, + (ulonglong) (hash_links * sizeof(HASH_LINK)), + &keycache->changed_blocks, + (ulonglong) (sizeof(BLOCK_LINK*) * + changed_blocks_hash_size), + &keycache->file_blocks, + (ulonglong) (sizeof(BLOCK_LINK*) * + changed_blocks_hash_size), + NullS)) + break; + my_large_free(keycache->block_mem, keycache->allocated_mem_size); + keycache->block_mem= 0; + } + if (blocks < 8) + { + my_errno= ENOMEM; + my_error(EE_OUTOFMEMORY, MYF(ME_FATAL), + blocks * keycache->key_cache_block_size); + goto err; + } + blocks= blocks / 4*3; + } + keycache->blocks_unused= blocks; + keycache->disk_blocks= (int) blocks; + keycache->hash_links= (int)hash_links; + keycache->hash_links_used= 0; + keycache->free_hash_list= NULL; + keycache->blocks_used= keycache->blocks_changed= 0; + + keycache->global_blocks_changed= 0; + keycache->blocks_available=0; /* For debugging */ + + /* The LRU chain is empty after initialization */ + keycache->used_last= NULL; + keycache->used_ins= NULL; + keycache->free_block_list= NULL; + keycache->keycache_time= 0; + keycache->warm_blocks= 0; + keycache->min_warm_blocks= (division_limit ? + blocks * division_limit / 100 + 1 : + blocks); + keycache->age_threshold= (age_threshold ? + blocks * age_threshold / 100 : + blocks); + keycache->changed_blocks_hash_size= changed_blocks_hash_size; + keycache->can_be_used= 1; + + keycache->waiting_for_hash_link.last_thread= NULL; + keycache->waiting_for_block.last_thread= NULL; + DBUG_PRINT("exit", + ("disk_blocks: %d block_root: %p hash_entries: %d\ + hash_root: %p hash_links: %d hash_link_root: %p", + keycache->disk_blocks, keycache->block_root, + keycache->hash_entries, keycache->hash_root, + keycache->hash_links, keycache->hash_link_root)); + } + else + { + /* key_buffer_size is specified too small. Disable the cache. */ + keycache->can_be_used= 0; + } + + keycache->blocks= keycache->disk_blocks > 0 ? keycache->disk_blocks : 0; + DBUG_RETURN((int) keycache->disk_blocks); + +err: + error= my_errno; + keycache->disk_blocks= 0; + keycache->blocks= 0; + if (keycache->block_mem) + { + my_large_free((uchar*) keycache->block_mem, keycache->allocated_mem_size); + keycache->block_mem= NULL; + } + if (keycache->block_root) + { + my_free(keycache->block_root); + keycache->block_root= NULL; + } + my_errno= error; + keycache->can_be_used= 0; + DBUG_RETURN(0); +} + + +/* + Prepare for resizing a simple key cache + + SYNOPSIS + prepare_resize_simple_key_cache() + keycache pointer to the control block of a simple key cache + release_lock <=> release the key cache lock before return + + DESCRIPTION + This function flushes all dirty pages from a simple key cache and after + this it destroys the key cache calling end_simple_key_cache. The function + takes the parameter keycache as a pointer to the control block + structure of the type SIMPLE_KEY_CACHE_CB for this key cache. + The parameter release_lock says whether the key cache lock must be + released before return from the function. + + RETURN VALUE + 0 - on success, + 1 - otherwise. + + NOTES + This function is the called by resize_simple_key_cache and + resize_partitioned_key_cache that resize simple and partitioned key caches + respectively. +*/ + +static +int prepare_resize_simple_key_cache(SIMPLE_KEY_CACHE_CB *keycache, + my_bool release_lock) +{ + int res= 0; + DBUG_ENTER("prepare_resize_simple_key_cache"); + + keycache_pthread_mutex_lock(&keycache->cache_lock); + + /* + We may need to wait for another thread which is doing a resize + already. This cannot happen in the MySQL server though. It allows + one resizer only. In set_var.cc keycache->in_init is used to block + multiple attempts. + */ + while (keycache->in_resize) + { + /* purecov: begin inspected */ + wait_on_queue(&keycache->resize_queue, &keycache->cache_lock); + /* purecov: end */ + } + + /* + Mark the operation in progress. This blocks other threads from doing + a resize in parallel. It prohibits new blocks to enter the cache. + Read/write requests can bypass the cache during the flush phase. + */ + keycache->in_resize= 1; + + /* Need to flush only if keycache is enabled. */ + if (keycache->can_be_used && keycache->disk_blocks != -1) + { + /* Start the flush phase. */ + keycache->resize_in_flush= 1; + + if (flush_all_key_blocks(keycache)) + { + /* TODO: if this happens, we should write a warning in the log file ! */ + keycache->resize_in_flush= 0; + keycache->can_be_used= 0; + res= 1; + goto finish; + } + DBUG_SLOW_ASSERT(cache_empty(keycache)); + + /* End the flush phase. */ + keycache->resize_in_flush= 0; + } + + /* + Some direct read/write operations (bypassing the cache) may still be + unfinished. Wait until they are done. If the key cache can be used, + direct I/O is done in increments of key_cache_block_size. That is, + every block is checked if it is in the cache. We need to wait for + pending I/O before re-initializing the cache, because we may change + the block size. Otherwise they could check for blocks at file + positions where the new block division has none. We do also want to + wait for I/O done when (if) the cache was disabled. It must not + run in parallel with normal cache operation. + */ + while (keycache->cnt_for_resize_op) + wait_on_queue(&keycache->waiting_for_resize_cnt, &keycache->cache_lock); + + end_simple_key_cache(keycache, 0); + +finish: + if (release_lock) + keycache_pthread_mutex_unlock(&keycache->cache_lock); + DBUG_RETURN(res); +} + + +/* + Finalize resizing a simple key cache + + SYNOPSIS + finish_resize_simple_key_cache() + keycache pointer to the control block of a simple key cache + + DESCRIPTION + This function performs finalizing actions for the operation of + resizing a simple key cache. The function takes the parameter + keycache as a pointer to the control block structure of the type + SIMPLE_KEY_CACHE_CB for this key cache. The function sets the flag + in_resize in this structure to FALSE. + + RETURN VALUE + none + + NOTES + This function is the called by resize_simple_key_cache and + resize_partitioned_key_cache that resize simple and partitioned key caches + respectively. +*/ + +static +void finish_resize_simple_key_cache(SIMPLE_KEY_CACHE_CB *keycache) +{ + DBUG_ENTER("finish_resize_simple_key_cache"); + + mysql_mutex_assert_owner(&keycache->cache_lock); + + /* + Mark the resize finished. This allows other threads to start a + resize or to request new cache blocks. + */ + keycache->in_resize= 0; + + + /* Signal waiting threads. */ + release_whole_queue(&keycache->resize_queue); + + + keycache_pthread_mutex_unlock(&keycache->cache_lock); + + DBUG_VOID_RETURN; +} + + +/* + Resize a simple key cache + + SYNOPSIS + resize_simple_key_cache() + keycache pointer to the control block of a simple key cache + key_cache_block_size size of blocks to keep cached data + use_mem memory to use for the key cache buffers/structures + division_limit new division limit (if not zero) + age_threshold new age threshold (if not zero) + + DESCRIPTION + This function is the implementation of the resize_key_cache interface + function that is employed by simple (non-partitioned) key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type SIMPLE_KEY_CACHE_CB for the simple key + cache to be resized. + The parameter key_cache_block_size specifies the new size of the blocks in + the key cache. The parameters division_limit and age_threshold + determine the new initial values of those characteristics of the key cache + that are used for midpoint insertion strategy. The parameter use_mem + specifies the total amount of memory to be allocated for key cache blocks + and auxiliary structures in the new key cache. + + RETURN VALUE + number of blocks in the key cache, if successful, + 0 - otherwise. + + NOTES. + The function first calls the function prepare_resize_simple_key_cache + to flush all dirty blocks from key cache, to free memory used + for key cache blocks and auxiliary structures. After this the + function builds a new key cache with new parameters. + + This implementation doesn't block the calls and executions of other + functions from the key cache interface. However it assumes that the + calls of resize_simple_key_cache itself are serialized. + + The function starts the operation only when all other threads + performing operations with the key cache let her to proceed + (when cnt_for_resize=0). +*/ + +static +int resize_simple_key_cache(SIMPLE_KEY_CACHE_CB *keycache, + uint key_cache_block_size, + size_t use_mem, uint division_limit, + uint age_threshold, uint changed_blocks_hash_size) +{ + int blocks= 0; + DBUG_ENTER("resize_simple_key_cache"); + + DBUG_ASSERT(keycache->key_cache_inited); + + /* + Note that the cache_lock mutex and the resize_queue are left untouched. + We do not lose the cache_lock and will release it only at the end of + this function. + */ + if (prepare_resize_simple_key_cache(keycache, 0)) + goto finish; + + /* The following will work even if use_mem is 0 */ + blocks= init_simple_key_cache(keycache, key_cache_block_size, use_mem, + division_limit, age_threshold, + changed_blocks_hash_size); + +finish: + finish_resize_simple_key_cache(keycache); + + DBUG_RETURN(blocks); +} + + +/* + Increment counter blocking resize key cache operation +*/ +static inline void inc_counter_for_resize_op(SIMPLE_KEY_CACHE_CB *keycache) +{ + keycache->cnt_for_resize_op++; +} + + +/* + Decrement counter blocking resize key cache operation; + Signal the operation to proceed when counter becomes equal zero +*/ +static inline void dec_counter_for_resize_op(SIMPLE_KEY_CACHE_CB *keycache) +{ + if (!--keycache->cnt_for_resize_op) + release_whole_queue(&keycache->waiting_for_resize_cnt); +} + + +/* + Change key cache parameters of a simple key cache + + SYNOPSIS + change_simple_key_cache_param() + keycache pointer to the control block of a simple key cache + division_limit new division limit (if not zero) + age_threshold new age threshold (if not zero) + + DESCRIPTION + This function is the implementation of the change_key_cache_param interface + function that is employed by simple (non-partitioned) key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type SIMPLE_KEY_CACHE_CB for the simple key + cache where new values of the division limit and the age threshold used + for midpoint insertion strategy are to be set. The parameters + division_limit and age_threshold provide these new values. + + RETURN VALUE + none + + NOTES. + Presently the function resets the key cache parameters concerning + midpoint insertion strategy - division_limit and age_threshold. + This function changes some parameters of a given key cache without + reformatting it. The function does not touch the contents the key + cache blocks. +*/ + +static +void change_simple_key_cache_param(SIMPLE_KEY_CACHE_CB *keycache, uint division_limit, + uint age_threshold) +{ + DBUG_ENTER("change_simple_key_cache_param"); + keycache_pthread_mutex_lock(&keycache->cache_lock); + if (division_limit) + keycache->min_warm_blocks= (keycache->disk_blocks * + division_limit / 100 + 1); + if (age_threshold) + keycache->age_threshold= (keycache->disk_blocks * + age_threshold / 100); + keycache_pthread_mutex_unlock(&keycache->cache_lock); + DBUG_VOID_RETURN; +} + + +/* + Destroy a simple key cache + + SYNOPSIS + end_simple_key_cache() + keycache pointer to the control block of a simple key cache + cleanup <=> complete free (free also mutex for key cache) + + DESCRIPTION + This function is the implementation of the end_key_cache interface + function that is employed by simple (non-partitioned) key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type SIMPLE_KEY_CACHE_CB for the simple key + cache to be destroyed. + The function frees the memory allocated for the key cache blocks and + auxiliary structures. If the value of the parameter cleanup is TRUE + then even the key cache mutex is freed. + + RETURN VALUE + none +*/ + +static +void end_simple_key_cache(SIMPLE_KEY_CACHE_CB *keycache, my_bool cleanup) +{ + DBUG_ENTER("end_simple_key_cache"); + DBUG_PRINT("enter", ("key_cache: %p", keycache)); + + if (!keycache->key_cache_inited) + DBUG_VOID_RETURN; + + if (keycache->disk_blocks > 0) + { + if (keycache->block_mem) + { + my_large_free((uchar*) keycache->block_mem, keycache->allocated_mem_size); + keycache->block_mem= NULL; + my_free(keycache->block_root); + keycache->block_root= NULL; + } + keycache->disk_blocks= -1; + /* Reset blocks_changed to be safe if flush_all_key_blocks is called */ + keycache->blocks_changed= 0; + } + + DBUG_PRINT("status", ("used: %lu changed: %lu w_requests: %lu " + "writes: %lu r_requests: %lu reads: %lu", + keycache->blocks_used, keycache->global_blocks_changed, + (ulong) keycache->global_cache_w_requests, + (ulong) keycache->global_cache_write, + (ulong) keycache->global_cache_r_requests, + (ulong) keycache->global_cache_read)); + + /* + Reset these values to be able to detect a disabled key cache. + See Bug#44068 (RESTORE can disable the MyISAM Key Cache). + */ + keycache->blocks_used= 0; + keycache->blocks_unused= 0; + + if (cleanup) + { + mysql_mutex_destroy(&keycache->cache_lock); + keycache->key_cache_inited= keycache->can_be_used= 0; + KEYCACHE_DEBUG_CLOSE; + } + DBUG_VOID_RETURN; +} /* end_key_cache */ + + +/* + Link a thread into double-linked queue of waiting threads. + + SYNOPSIS + link_into_queue() + wqueue pointer to the queue structure + thread pointer to the thread to be added to the queue + + RETURN VALUE + none + + NOTES. + Queue is represented by a circular list of the thread structures + The list is double-linked of the type (**prev,*next), accessed by + a pointer to the last element. +*/ + +static void link_into_queue(KEYCACHE_WQUEUE *wqueue, + struct st_my_thread_var *thread) +{ + struct st_my_thread_var *last; + DBUG_ASSERT(!thread->next && !thread->prev); + + if (! (last= wqueue->last_thread)) + { + /* Queue is empty */ + thread->next= thread; + thread->prev= &thread->next; + } + else + { + DBUG_ASSERT(last->next->prev == &last->next); + /* Add backlink to previous element */ + thread->prev= last->next->prev; + /* Fix first in list to point backwords to current */ + last->next->prev= &thread->next; + /* Next should point to the first element in list */ + thread->next= last->next; + /* Fix old element to point to new one */ + last->next= thread; + } + wqueue->last_thread= thread; +} + +/* + Unlink a thread from double-linked queue of waiting threads + + SYNOPSIS + unlink_from_queue() + wqueue pointer to the queue structure + thread pointer to the thread to be removed from the queue + + RETURN VALUE + none + + NOTES. + See NOTES for link_into_queue +*/ + +static void unlink_from_queue(KEYCACHE_WQUEUE *wqueue, + struct st_my_thread_var *thread) +{ + KEYCACHE_DBUG_PRINT("unlink_from_queue", ("thread %ld", (ulong) thread->id)); + DBUG_ASSERT(thread->next && thread->prev); + + if (thread->next == thread) + { + /* The queue contains only one member */ + wqueue->last_thread= NULL; + } + else + { + /* Remove current element from list */ + thread->next->prev= thread->prev; + *thread->prev= thread->next; + /* If first element, change list pointer to point to previous element */ + if (wqueue->last_thread == thread) + wqueue->last_thread= STRUCT_PTR(struct st_my_thread_var, next, + thread->prev); + } + thread->next= NULL; +#ifdef DBUG_ASSERT_EXISTS + /* + This makes it easier to see it's not in a chain during debugging. + And some DBUG_ASSERT() rely on it. + */ + thread->prev= NULL; +#endif +} + + +/* + Add a thread to single-linked queue of waiting threads + + SYNOPSIS + wait_on_queue() + wqueue Pointer to the queue structure. + mutex Cache_lock to acquire after awake. + + RETURN VALUE + none + + NOTES. + Queue is represented by a circular list of the thread structures + The list is single-linked of the type (*next), accessed by a pointer + to the last element. + + The function protects against stray signals by verifying that the + current thread is unlinked from the queue when awaking. However, + since several threads can wait for the same event, it might be + necessary for the caller of the function to check again if the + condition for awake is indeed matched. +*/ + +static void wait_on_queue(KEYCACHE_WQUEUE *wqueue, + mysql_mutex_t *mutex) +{ + struct st_my_thread_var *last; + struct st_my_thread_var *thread= my_thread_var; + DBUG_ASSERT(!thread->next); + DBUG_ASSERT(!thread->prev); /* Not required, but must be true anyway. */ + mysql_mutex_assert_owner(mutex); + + /* Add to queue. */ + if (! (last= wqueue->last_thread)) + thread->next= thread; + else + { + thread->next= last->next; + last->next= thread; + } + wqueue->last_thread= thread; + + /* + Wait until thread is removed from queue by the signaling thread. + The loop protects against stray signals. + */ + do + { + KEYCACHE_DBUG_PRINT("wait", ("suspend thread %ld", (ulong) thread->id)); + keycache_pthread_cond_wait(&thread->suspend, mutex); + } + while (thread->next); +} + + +/* + Remove all threads from queue signaling them to proceed + + SYNOPSIS + release_whole_queue() + wqueue pointer to the queue structure + + RETURN VALUE + none + + NOTES. + See notes for wait_on_queue(). + When removed from the queue each thread is signaled via condition + variable thread->suspend. +*/ + +static void release_whole_queue(KEYCACHE_WQUEUE *wqueue) +{ + struct st_my_thread_var *last; + struct st_my_thread_var *next; + struct st_my_thread_var *thread; + + /* Queue may be empty. */ + if (!(last= wqueue->last_thread)) + return; + + next= last->next; /* First (oldest) element */ + do + { + thread=next; + DBUG_ASSERT(thread && thread->init == 1); + KEYCACHE_DBUG_PRINT("release_whole_queue: signal", + ("thread %ld", (ulong) thread->id)); + /* Take thread from queue. */ + next= thread->next; + thread->next= NULL; + + /* Signal the thread. */ + keycache_pthread_cond_signal(&thread->suspend); + } + while (thread != last); + + /* Now queue is definitely empty. */ + wqueue->last_thread= NULL; +} + + +/* + Unlink a block from the chain of dirty/clean blocks +*/ + +static inline void unlink_changed(BLOCK_LINK *block) +{ + DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); + if (block->next_changed) + block->next_changed->prev_changed= block->prev_changed; + *block->prev_changed= block->next_changed; + +#ifdef DBUG_ASSERT_EXISTS + /* + This makes it easier to see it's not in a chain during debugging. + And some DBUG_ASSERT() rely on it. + */ + block->next_changed= NULL; + block->prev_changed= NULL; +#endif +} + + +/* + Link a block into the chain of dirty/clean blocks +*/ + +static inline void link_changed(BLOCK_LINK *block, BLOCK_LINK **phead) +{ + DBUG_ASSERT(!block->next_changed); + DBUG_ASSERT(!block->prev_changed); + block->prev_changed= phead; + if ((block->next_changed= *phead)) + (*phead)->prev_changed= &block->next_changed; + *phead= block; +} + + +/* + Link a block in a chain of clean blocks of a file. + + SYNOPSIS + link_to_file_list() + keycache Key cache handle + block Block to relink + file File to be linked to + unlink If to unlink first + + DESCRIPTION + Unlink a block from whichever chain it is linked in, if it's + asked for, and link it to the chain of clean blocks of the + specified file. + + NOTE + Please do never set/clear BLOCK_CHANGED outside of + link_to_file_list() or link_to_changed_list(). + You would risk to damage correct counting of changed blocks + and to find blocks in the wrong hash. + + RETURN + void +*/ + +static void link_to_file_list(SIMPLE_KEY_CACHE_CB *keycache, + BLOCK_LINK *block, int file, + my_bool unlink_block) +{ + DBUG_ASSERT(block->status & BLOCK_IN_USE); + DBUG_ASSERT(block->hash_link && block->hash_link->block == block); + DBUG_ASSERT(block->hash_link->file == file); + if (unlink_block) + unlink_changed(block); + link_changed(block, &keycache->file_blocks[FILE_HASH(file, keycache)]); + if (block->status & BLOCK_CHANGED) + { + block->status&= ~BLOCK_CHANGED; + keycache->blocks_changed--; + keycache->global_blocks_changed--; + } +} + + +/* + Re-link a block from the clean chain to the dirty chain of a file. + + SYNOPSIS + link_to_changed_list() + keycache key cache handle + block block to relink + + DESCRIPTION + Unlink a block from the chain of clean blocks of a file + and link it to the chain of dirty blocks of the same file. + + NOTE + Please do never set/clear BLOCK_CHANGED outside of + link_to_file_list() or link_to_changed_list(). + You would risk to damage correct counting of changed blocks + and to find blocks in the wrong hash. + + RETURN + void +*/ + +static void link_to_changed_list(SIMPLE_KEY_CACHE_CB *keycache, + BLOCK_LINK *block) +{ + DBUG_ASSERT(block->status & BLOCK_IN_USE); + DBUG_ASSERT(!(block->status & BLOCK_CHANGED)); + DBUG_ASSERT(block->hash_link && block->hash_link->block == block); + + unlink_changed(block); + link_changed(block, + &keycache->changed_blocks[FILE_HASH(block->hash_link->file, keycache)]); + block->status|=BLOCK_CHANGED; + keycache->blocks_changed++; + keycache->global_blocks_changed++; +} + + +/* + Link a block to the LRU chain at the beginning or at the end of + one of two parts. + + SYNOPSIS + link_block() + keycache pointer to a key cache data structure + block pointer to the block to link to the LRU chain + hot <-> to link the block into the hot subchain + at_end <-> to link the block at the end of the subchain + + RETURN VALUE + none + + NOTES. + The LRU ring is represented by a circular list of block structures. + The list is double-linked of the type (**prev,*next) type. + The LRU ring is divided into two parts - hot and warm. + There are two pointers to access the last blocks of these two + parts. The beginning of the warm part follows right after the + end of the hot part. + Only blocks of the warm part can be used for eviction. + The first block from the beginning of this subchain is always + taken for eviction (keycache->last_used->next) + + LRU chain: +------+ H O T +------+ + +----| end |----...<----| beg |----+ + | +------+last +------+ | + v<-link in latest hot (new end) | + | link in latest warm (new end)->^ + | +------+ W A R M +------+ | + +----| beg |---->...----| end |----+ + +------+ +------+ins + first for eviction + + It is also possible that the block is selected for eviction and thus + not linked in the LRU ring. +*/ + +static void link_block(SIMPLE_KEY_CACHE_CB *keycache, BLOCK_LINK *block, + my_bool hot, my_bool at_end) +{ + BLOCK_LINK *ins; + BLOCK_LINK **pins; + + DBUG_ASSERT((block->status & ~BLOCK_CHANGED) == (BLOCK_READ | BLOCK_IN_USE)); + DBUG_ASSERT(block->hash_link); /*backptr to block NULL from free_block()*/ + DBUG_ASSERT(!block->requests); + DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); + DBUG_ASSERT(!block->next_used); + DBUG_ASSERT(!block->prev_used); + if (!hot && keycache->waiting_for_block.last_thread) + { + /* Signal that in the LRU warm sub-chain an available block has appeared */ + struct st_my_thread_var *last_thread= + keycache->waiting_for_block.last_thread; + struct st_my_thread_var *first_thread= last_thread->next; + struct st_my_thread_var *next_thread= first_thread; + HASH_LINK *hash_link= (HASH_LINK *) first_thread->keycache_link; + struct st_my_thread_var *thread; + do + { + thread= next_thread; + next_thread= thread->next; + /* + We notify about the event all threads that ask + for the same page as the first thread in the queue + */ + if ((HASH_LINK *) thread->keycache_link == hash_link) + { + KEYCACHE_DBUG_PRINT("link_block: signal", + ("thread %ld", (ulong) thread->id)); + keycache_pthread_cond_signal(&thread->suspend); + unlink_from_queue(&keycache->waiting_for_block, thread); + block->requests++; + } + } + while (thread != last_thread); + hash_link->block= block; + /* + NOTE: We assigned the block to the hash_link and signalled the + requesting thread(s). But it is possible that other threads runs + first. These threads see the hash_link assigned to a block which + is assigned to another hash_link and not marked BLOCK_IN_SWITCH. + This can be a problem for functions that do not select the block + via its hash_link: flush and free. They do only see a block which + is in a "normal" state and don't know that it will be evicted soon. + + We cannot set BLOCK_IN_SWITCH here because only one of the + requesting threads must handle the eviction. All others must wait + for it to complete. If we set the flag here, the threads would not + know who is in charge of the eviction. Without the flag, the first + thread takes the stick and sets the flag. + + But we need to note in the block that is has been selected for + eviction. It must not be freed. The evicting thread will not + expect the block in the free list. Before freeing we could also + check if block->requests > 1. But I think including another flag + in the check of block->status is slightly more efficient and + probably easier to read. + */ + block->status|= BLOCK_IN_EVICTION; + KEYCACHE_THREAD_TRACE("link_block: after signaling"); +#if defined(KEYCACHE_DEBUG) + KEYCACHE_DBUG_PRINT("link_block", + ("linked,unlinked block %u status=%x #requests=%u #available=%u", + BLOCK_NUMBER(block), block->status, + block->requests, keycache->blocks_available)); +#endif + return; + } + pins= hot ? &keycache->used_ins : &keycache->used_last; + ins= *pins; + if (ins) + { + ins->next_used->prev_used= &block->next_used; + block->next_used= ins->next_used; + block->prev_used= &ins->next_used; + ins->next_used= block; + if (at_end) + *pins= block; + } + else + { + /* The LRU ring is empty. Let the block point to itself. */ + keycache->used_last= keycache->used_ins= block->next_used= block; + block->prev_used= &block->next_used; + } + KEYCACHE_THREAD_TRACE("link_block"); +#if defined(KEYCACHE_DEBUG) + keycache->blocks_available++; + KEYCACHE_DBUG_PRINT("link_block", + ("linked block %u:%1u status=%x #requests=%u #available=%u", + BLOCK_NUMBER(block), at_end, block->status, + block->requests, keycache->blocks_available)); + KEYCACHE_DBUG_ASSERT((ulong) keycache->blocks_available <= + keycache->blocks_used); +#endif +} + + +/* + Unlink a block from the LRU chain + + SYNOPSIS + unlink_block() + keycache pointer to a key cache data structure + block pointer to the block to unlink from the LRU chain + + RETURN VALUE + none + + NOTES. + See NOTES for link_block +*/ + +static void unlink_block(SIMPLE_KEY_CACHE_CB *keycache, BLOCK_LINK *block) +{ + DBUG_ASSERT((block->status & ~BLOCK_CHANGED) == (BLOCK_READ | BLOCK_IN_USE)); + DBUG_ASSERT(block->hash_link); /*backptr to block NULL from free_block()*/ + DBUG_ASSERT(!block->requests); + DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); + DBUG_ASSERT(block->next_used && block->prev_used && + (block->next_used->prev_used == &block->next_used) && + (*block->prev_used == block)); + if (block->next_used == block) + /* The list contains only one member */ + keycache->used_last= keycache->used_ins= NULL; + else + { + block->next_used->prev_used= block->prev_used; + *block->prev_used= block->next_used; + if (keycache->used_last == block) + keycache->used_last= STRUCT_PTR(BLOCK_LINK, next_used, block->prev_used); + if (keycache->used_ins == block) + keycache->used_ins=STRUCT_PTR(BLOCK_LINK, next_used, block->prev_used); + } + block->next_used= NULL; +#ifdef DBUG_ASSERT_EXISTS + /* + This makes it easier to see it's not in a chain during debugging. + And some DBUG_ASSERT() rely on it. + */ + block->prev_used= NULL; +#endif + + KEYCACHE_THREAD_TRACE("unlink_block"); +#if defined(KEYCACHE_DEBUG) + KEYCACHE_DBUG_ASSERT(keycache->blocks_available != 0); + keycache->blocks_available--; + KEYCACHE_DBUG_PRINT("unlink_block", + ("unlinked block %u status=%x #requests=%u #available=%u", + BLOCK_NUMBER(block), block->status, + block->requests, keycache->blocks_available)); +#endif +} + + +/* + Register requests for a block. + + SYNOPSIS + reg_requests() + keycache Pointer to a key cache data structure. + block Pointer to the block to register a request on. + count Number of requests. Always 1. + + NOTE + The first request unlinks the block from the LRU ring. This means + that it is protected against eveiction. + + RETURN + void +*/ +static void reg_requests(SIMPLE_KEY_CACHE_CB *keycache, + BLOCK_LINK *block, int count) +{ + DBUG_ASSERT(block->status & BLOCK_IN_USE); + DBUG_ASSERT(block->hash_link); + + if (!block->requests) + unlink_block(keycache, block); + block->requests+=count; +} + + +/* + Unregister request for a block + linking it to the LRU chain if it's the last request + + SYNOPSIS + unreg_request() + keycache pointer to a key cache data structure + block pointer to the block to link to the LRU chain + at_end <-> to link the block at the end of the LRU chain + + RETURN VALUE + none + + NOTES. + Every linking to the LRU ring decrements by one a special block + counter (if it's positive). If the at_end parameter is TRUE the block is + added either at the end of warm sub-chain or at the end of hot sub-chain. + It is added to the hot subchain if its counter is zero and number of + blocks in warm sub-chain is not less than some low limit (determined by + the division_limit parameter). Otherwise the block is added to the warm + sub-chain. If the at_end parameter is FALSE the block is always added + at beginning of the warm sub-chain. + Thus a warm block can be promoted to the hot sub-chain when its counter + becomes zero for the first time. + At the same time the block at the very beginning of the hot subchain + might be moved to the beginning of the warm subchain if it stays untouched + for a too long time (this time is determined by parameter age_threshold). + + It is also possible that the block is selected for eviction and thus + not linked in the LRU ring. +*/ + +static void unreg_request(SIMPLE_KEY_CACHE_CB *keycache, + BLOCK_LINK *block, int at_end) +{ + DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); + DBUG_ASSERT(block->hash_link); /*backptr to block NULL from free_block()*/ + DBUG_ASSERT(block->requests); + DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); + DBUG_ASSERT(!block->next_used); + DBUG_ASSERT(!block->prev_used); + /* + Unregister the request, but do not link erroneous blocks into the + LRU ring. + */ + if (!--block->requests && !(block->status & BLOCK_ERROR)) + { + my_bool hot; + if (block->hits_left) + block->hits_left--; + hot= !block->hits_left && at_end && + keycache->warm_blocks > keycache->min_warm_blocks; + if (hot) + { + if (block->temperature == BLOCK_WARM) + keycache->warm_blocks--; + block->temperature= BLOCK_HOT; + KEYCACHE_DBUG_PRINT("unreg_request", ("#warm_blocks: %lu", + keycache->warm_blocks)); + } + link_block(keycache, block, hot, (my_bool)at_end); + block->last_hit_time= keycache->keycache_time; + keycache->keycache_time++; + /* + At this place, the block might be in the LRU ring or not. If an + evicter was waiting for a block, it was selected for eviction and + not linked in the LRU ring. + */ + + /* + Check if we should link a hot block to the warm block sub-chain. + It is possible that we select the same block as above. But it can + also be another block. In any case a block from the LRU ring is + selected. In other words it works even if the above block was + selected for eviction and not linked in the LRU ring. Since this + happens only if the LRU ring is empty, the block selected below + would be NULL and the rest of the function skipped. + */ + block= keycache->used_ins; + if (block && keycache->keycache_time - block->last_hit_time > + keycache->age_threshold) + { + unlink_block(keycache, block); + link_block(keycache, block, 0, 0); + if (block->temperature != BLOCK_WARM) + { + keycache->warm_blocks++; + block->temperature= BLOCK_WARM; + } + KEYCACHE_DBUG_PRINT("unreg_request", ("#warm_blocks: %lu", + keycache->warm_blocks)); + } + } +} + +/* + Remove a reader of the page in block +*/ + +static void remove_reader(BLOCK_LINK *block) +{ + DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); + DBUG_ASSERT(block->hash_link && block->hash_link->block == block); + DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); + DBUG_ASSERT(!block->next_used); + DBUG_ASSERT(!block->prev_used); + DBUG_ASSERT(block->hash_link->requests); + if (! --block->hash_link->requests && block->condvar) + keycache_pthread_cond_signal(block->condvar); +} + + +/* + Wait until the last reader of the page in block + signals on its termination +*/ + +static void wait_for_readers(SIMPLE_KEY_CACHE_CB *keycache, + BLOCK_LINK *block) +{ + struct st_my_thread_var *thread= my_thread_var; + DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); + DBUG_ASSERT(!(block->status & (BLOCK_IN_FLUSH | BLOCK_CHANGED))); + DBUG_ASSERT(block->hash_link); + DBUG_ASSERT(block->hash_link->block == block); + /* Linked in file_blocks or changed_blocks hash. */ + DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); + /* Not linked in LRU ring. */ + DBUG_ASSERT(!block->next_used); + DBUG_ASSERT(!block->prev_used); + while (block->hash_link->requests) + { + KEYCACHE_DBUG_PRINT("wait_for_readers: wait", + ("suspend thread %ld block %u", + (ulong) thread->id, BLOCK_NUMBER(block))); + /* There must be no other waiter. We have no queue here. */ + DBUG_ASSERT(!block->condvar); + block->condvar= &thread->suspend; + keycache_pthread_cond_wait(&thread->suspend, &keycache->cache_lock); + block->condvar= NULL; + } +} + + +/* + Add a hash link to a bucket in the hash_table +*/ + +static inline void link_hash(HASH_LINK **start, HASH_LINK *hash_link) +{ + if (*start) + (*start)->prev= &hash_link->next; + hash_link->next= *start; + hash_link->prev= start; + *start= hash_link; +} + + +/* + Remove a hash link from the hash table +*/ + +static void unlink_hash(SIMPLE_KEY_CACHE_CB *keycache, HASH_LINK *hash_link) +{ + KEYCACHE_DBUG_PRINT("unlink_hash", ("fd: %u pos_ %lu #requests=%u", + (uint) hash_link->file,(ulong) hash_link->diskpos, hash_link->requests)); + KEYCACHE_DBUG_ASSERT(hash_link->requests == 0); + if ((*hash_link->prev= hash_link->next)) + hash_link->next->prev= hash_link->prev; + hash_link->block= NULL; + if (keycache->waiting_for_hash_link.last_thread) + { + /* Signal that a free hash link has appeared */ + struct st_my_thread_var *last_thread= + keycache->waiting_for_hash_link.last_thread; + struct st_my_thread_var *first_thread= last_thread->next; + struct st_my_thread_var *next_thread= first_thread; + KEYCACHE_PAGE *first_page= (KEYCACHE_PAGE *) (first_thread->keycache_link); + struct st_my_thread_var *thread; + + hash_link->file= first_page->file; + hash_link->diskpos= first_page->filepos; + do + { + KEYCACHE_PAGE *page; + thread= next_thread; + page= (KEYCACHE_PAGE *) thread->keycache_link; + next_thread= thread->next; + /* + We notify about the event all threads that ask + for the same page as the first thread in the queue + */ + if (page->file == hash_link->file && page->filepos == hash_link->diskpos) + { + KEYCACHE_DBUG_PRINT("unlink_hash: signal", + ("thread %ld", (ulong) thread->id)); + keycache_pthread_cond_signal(&thread->suspend); + unlink_from_queue(&keycache->waiting_for_hash_link, thread); + } + } + while (thread != last_thread); + link_hash(&keycache->hash_root[KEYCACHE_HASH(hash_link->file, + hash_link->diskpos)], + hash_link); + return; + } + hash_link->next= keycache->free_hash_list; + keycache->free_hash_list= hash_link; +} + + +/* + Get the hash link for a page +*/ + +static HASH_LINK *get_hash_link(SIMPLE_KEY_CACHE_CB *keycache, + int file, my_off_t filepos) +{ + reg1 HASH_LINK *hash_link, **start; +#if defined(KEYCACHE_DEBUG) + int cnt; +#endif + + KEYCACHE_DBUG_PRINT("get_hash_link", ("fd: %u pos: %lu", + (uint) file,(ulong) filepos)); + +restart: + /* + Find the bucket in the hash table for the pair (file, filepos); + start contains the head of the bucket list, + hash_link points to the first member of the list + */ + hash_link= *(start= &keycache->hash_root[KEYCACHE_HASH(file, filepos)]); +#if defined(KEYCACHE_DEBUG) + cnt= 0; +#endif + /* Look for an element for the pair (file, filepos) in the bucket chain */ + while (hash_link && + (hash_link->diskpos != filepos || hash_link->file != file)) + { + hash_link= hash_link->next; +#if defined(KEYCACHE_DEBUG) + cnt++; + if (! (cnt <= keycache->hash_links_used)) + { + int i; + for (i=0, hash_link= *start ; + i < cnt ; i++, hash_link= hash_link->next) + { + KEYCACHE_DBUG_PRINT("get_hash_link", ("fd: %u pos: %lu", + (uint) hash_link->file,(ulong) hash_link->diskpos)); + } + } + KEYCACHE_DBUG_ASSERT(cnt <= keycache->hash_links_used); +#endif + } + if (! hash_link) + { + /* There is no hash link in the hash table for the pair (file, filepos) */ + if (keycache->free_hash_list) + { + hash_link= keycache->free_hash_list; + keycache->free_hash_list= hash_link->next; + } + else if (keycache->hash_links_used < keycache->hash_links) + { + hash_link= &keycache->hash_link_root[keycache->hash_links_used++]; + } + else + { + /* Wait for a free hash link */ + struct st_my_thread_var *thread= my_thread_var; + KEYCACHE_PAGE page; + KEYCACHE_DBUG_PRINT("get_hash_link", ("waiting")); + page.file= file; + page.filepos= filepos; + thread->keycache_link= (void *) &page; + link_into_queue(&keycache->waiting_for_hash_link, thread); + KEYCACHE_DBUG_PRINT("get_hash_link: wait", + ("suspend thread %ld", (ulong) thread->id)); + keycache_pthread_cond_wait(&thread->suspend, + &keycache->cache_lock); + thread->keycache_link= NULL; + goto restart; + } + hash_link->file= file; + hash_link->diskpos= filepos; + link_hash(start, hash_link); + } + /* Register the request for the page */ + hash_link->requests++; + + return hash_link; +} + + +/* + Get a block for the file page requested by a keycache read/write operation; + If the page is not in the cache return a free block, if there is none + return the lru block after saving its buffer if the page is dirty. + + SYNOPSIS + + find_key_block() + keycache pointer to a key cache data structure + file handler for the file to read page from + filepos position of the page in the file + init_hits_left how initialize the block counter for the page + wrmode <-> get for writing + page_st out {PAGE_READ,PAGE_TO_BE_READ,PAGE_WAIT_TO_BE_READ} + + RETURN VALUE + Pointer to the found block if successful, 0 - otherwise + + NOTES. + For the page from file positioned at filepos the function checks whether + the page is in the key cache specified by the first parameter. + If this is the case it immediately returns the block. + If not, the function first chooses a block for this page. If there is + no not used blocks in the key cache yet, the function takes the block + at the very beginning of the warm sub-chain. It saves the page in that + block if it's dirty before returning the pointer to it. + The function returns in the page_st parameter the following values: + PAGE_READ - if page already in the block, + PAGE_TO_BE_READ - if it is to be read yet by the current thread + WAIT_TO_BE_READ - if it is to be read by another thread + If an error occurs THE BLOCK_ERROR bit is set in the block status. + It might happen that there are no blocks in LRU chain (in warm part) - + all blocks are unlinked for some read/write operations. Then the function + waits until first of this operations links any block back. +*/ + +static BLOCK_LINK *find_key_block(SIMPLE_KEY_CACHE_CB *keycache, + File file, my_off_t filepos, + int init_hits_left, + int wrmode, int *page_st) +{ + HASH_LINK *hash_link; + BLOCK_LINK *block; + int error= 0; + int page_status; + + DBUG_ENTER("find_key_block"); + KEYCACHE_THREAD_TRACE("find_key_block:begin"); + DBUG_PRINT("enter", ("fd: %d pos: %lu wrmode: %d", + file, (ulong) filepos, wrmode)); + KEYCACHE_DBUG_PRINT("find_key_block", ("fd: %d pos: %lu wrmode: %d", + file, (ulong) filepos, + wrmode)); +#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG) + DBUG_EXECUTE("check_keycache2", + test_key_cache(keycache, "start of find_key_block", 0);); +#endif + +restart: + /* + If the flush phase of a resize operation fails, the cache is left + unusable. This will be detected only after "goto restart". + */ + if (!keycache->can_be_used) + DBUG_RETURN(0); + + /* + Find the hash_link for the requested file block (file, filepos). We + do always get a hash_link here. It has registered our request so + that no other thread can use it for another file block until we + release the request (which is done by remove_reader() usually). The + hash_link can have a block assigned to it or not. If there is a + block, it may be assigned to this hash_link or not. In cases where a + block is evicted from the cache, it is taken from the LRU ring and + referenced by the new hash_link. But the block can still be assigned + to its old hash_link for some time if it needs to be flushed first, + or if there are other threads still reading it. + + Summary: + hash_link is always returned. + hash_link->block can be: + - NULL or + - not assigned to this hash_link or + - assigned to this hash_link. If assigned, the block can have + - invalid data (when freshly assigned) or + - valid data. Valid data can be + - changed over the file contents (dirty) or + - not changed (clean). + */ + hash_link= get_hash_link(keycache, file, filepos); + DBUG_ASSERT((hash_link->file == file) && (hash_link->diskpos == filepos)); + + page_status= -1; + if ((block= hash_link->block) && + block->hash_link == hash_link && (block->status & BLOCK_READ)) + { + /* Assigned block with valid (changed or unchanged) contents. */ + page_status= PAGE_READ; + } + /* + else (page_status == -1) + - block == NULL or + - block not assigned to this hash_link or + - block assigned but not yet read from file (invalid data). + */ + + if (keycache->in_resize) + { + /* This is a request during a resize operation */ + + if (!block) + { + struct st_my_thread_var *thread; + + /* + The file block is not in the cache. We don't need it in the + cache: we are going to read or write directly to file. Cancel + the request. We can simply decrement hash_link->requests because + we did not release cache_lock since increasing it. So no other + thread can wait for our request to become released. + */ + if (hash_link->requests == 1) + { + /* + We are the only one to request this hash_link (this file/pos). + Free the hash_link. + */ + hash_link->requests--; + unlink_hash(keycache, hash_link); + DBUG_RETURN(0); + } + + /* + More requests on the hash_link. Someone tries to evict a block + for this hash_link (could have started before resizing started). + This means that the LRU ring is empty. Otherwise a block could + be assigned immediately. Behave like a thread that wants to + evict a block for this file/pos. Add to the queue of threads + waiting for a block. Wait until there is one assigned. + + Refresh the request on the hash-link so that it cannot be reused + for another file/pos. + */ + thread= my_thread_var; + thread->keycache_link= (void *) hash_link; + link_into_queue(&keycache->waiting_for_block, thread); + do + { + KEYCACHE_DBUG_PRINT("find_key_block: wait", + ("suspend thread %ld", (ulong) thread->id)); + keycache_pthread_cond_wait(&thread->suspend, + &keycache->cache_lock); + } while (thread->next); + thread->keycache_link= NULL; + /* + A block should now be assigned to the hash_link. But it may + still need to be evicted. Anyway, we should re-check the + situation. page_status must be set correctly. + */ + hash_link->requests--; + goto restart; + } /* end of if (!block) */ + + /* + There is a block for this file/pos in the cache. Register a + request on it. This unlinks it from the LRU ring (if it is there) + and hence protects it against eviction (if not already in + eviction). We need this for returning the block to the caller, for + calling remove_reader() (for debugging purposes), and for calling + free_block(). The only case where we don't need the request is if + the block is in eviction. In that case we have to unregister the + request later. + */ + reg_requests(keycache, block, 1); + + if (page_status != PAGE_READ) + { + /* + - block not assigned to this hash_link or + - block assigned but not yet read from file (invalid data). + + This must be a block in eviction. It will be read soon. We need + to wait here until this happened. Otherwise the caller could + access a wrong block or a block which is in read. While waiting + we cannot lose hash_link nor block. We have registered a request + on the hash_link. Everything can happen to the block but changes + in the hash_link -> block relationship. In other words: + everything can happen to the block but free or another completed + eviction. + + Note that we bahave like a secondary requestor here. We just + cannot return with PAGE_WAIT_TO_BE_READ. This would work for + read requests and writes on dirty blocks that are not in flush + only. Waiting here on COND_FOR_REQUESTED works in all + situations. + */ + DBUG_ASSERT(((block->hash_link != hash_link) && + (block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))) || + ((block->hash_link == hash_link) && + !(block->status & BLOCK_READ))); + wait_on_queue(&block->wqueue[COND_FOR_REQUESTED], &keycache->cache_lock); + /* + Here we can trust that the block has been assigned to this + hash_link (block->hash_link == hash_link) and read into the + buffer (BLOCK_READ). The worst things possible here are that the + block is in free (BLOCK_REASSIGNED). But the block is still + assigned to the hash_link. The freeing thread waits until we + release our request on the hash_link. The block must not be + again in eviction because we registered an request on it before + starting to wait. + */ + DBUG_ASSERT(block->hash_link == hash_link); + DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); + DBUG_ASSERT(!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))); + } + /* + The block is in the cache. Assigned to the hash_link. Valid data. + Note that in case of page_st == PAGE_READ, the block can be marked + for eviction. In any case it can be marked for freeing. + */ + + if (!wrmode) + { + /* A reader can just read the block. */ + *page_st= PAGE_READ; + DBUG_ASSERT((hash_link->file == file) && + (hash_link->diskpos == filepos) && + (block->hash_link == hash_link)); + DBUG_RETURN(block); + } + + /* + This is a writer. No two writers for the same block can exist. + This must be assured by locks outside of the key cache. + */ + DBUG_ASSERT(!(block->status & BLOCK_FOR_UPDATE) || fail_block(block)); + + while (block->status & BLOCK_IN_FLUSH) + { + /* + Wait until the block is flushed to file. Do not release the + request on the hash_link yet to prevent that the block is freed + or reassigned while we wait. While we wait, several things can + happen to the block, including another flush. But the block + cannot be reassigned to another hash_link until we release our + request on it. But it can be marked BLOCK_REASSIGNED from free + or eviction, while they wait for us to release the hash_link. + */ + wait_on_queue(&block->wqueue[COND_FOR_SAVED], &keycache->cache_lock); + /* + If the flush phase failed, the resize could have finished while + we waited here. + */ + if (!keycache->in_resize) + { + remove_reader(block); + unreg_request(keycache, block, 1); + goto restart; + } + DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); + DBUG_ASSERT(!(block->status & BLOCK_FOR_UPDATE) || fail_block(block)); + DBUG_ASSERT(block->hash_link == hash_link); + } + + if (block->status & BLOCK_CHANGED) + { + /* + We want to write a block with changed contents. If the cache + block size is bigger than the callers block size (e.g. MyISAM), + the caller may replace part of the block only. Changes of the + other part of the block must be preserved. Since the block has + not yet been selected for flush, we can still add our changes. + */ + *page_st= PAGE_READ; + DBUG_ASSERT((hash_link->file == file) && + (hash_link->diskpos == filepos) && + (block->hash_link == hash_link)); + DBUG_RETURN(block); + } + + /* + This is a write request for a clean block. We do not want to have + new dirty blocks in the cache while resizing. We will free the + block and write directly to file. If the block is in eviction or + in free, we just let it go. + + Unregister from the hash_link. This must be done before freeing + the block. And it must be done if not freeing the block. Because + we could have waited above, we need to call remove_reader(). Other + threads could wait for us to release our request on the hash_link. + */ + remove_reader(block); + + /* If the block is not in eviction and not in free, we can free it. */ + if (!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | + BLOCK_REASSIGNED))) + { + /* + Free block as we are going to write directly to file. + Although we have an exlusive lock for the updated key part, + the control can be yielded by the current thread as we might + have unfinished readers of other key parts in the block + buffer. Still we are guaranteed not to have any readers + of the key part we are writing into until the block is + removed from the cache as we set the BLOCK_REASSIGNED + flag (see the code below that handles reading requests). + */ + free_block(keycache, block); + } + else + { + /* + The block will be evicted/freed soon. Don't touch it in any way. + Unregister the request that we registered above. + */ + unreg_request(keycache, block, 1); + + /* + The block is still assigned to the hash_link (the file/pos that + we are going to write to). Wait until the eviction/free is + complete. Otherwise the direct write could complete before all + readers are done with the block. So they could read outdated + data. + + Since we released our request on the hash_link, it can be reused + for another file/pos. Hence we cannot just check for + block->hash_link == hash_link. As long as the resize is + proceeding the block cannot be reassigned to the same file/pos + again. So we can terminate the loop when the block is no longer + assigned to this file/pos. + */ + do + { + wait_on_queue(&block->wqueue[COND_FOR_SAVED], + &keycache->cache_lock); + /* + If the flush phase failed, the resize could have finished + while we waited here. + */ + if (!keycache->in_resize) + goto restart; + } while (block->hash_link && + (block->hash_link->file == file) && + (block->hash_link->diskpos == filepos)); + } + DBUG_RETURN(0); + } + + if (page_status == PAGE_READ && + (block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | + BLOCK_REASSIGNED))) + { + /* + This is a request for a block to be removed from cache. The block + is assigned to this hash_link and contains valid data, but is + marked for eviction or to be freed. Possible reasons why it has + not yet been evicted/freed can be a flush before reassignment + (BLOCK_IN_SWITCH), readers of the block have not finished yet + (BLOCK_REASSIGNED), or the evicting thread did not yet awake after + the block has been selected for it (BLOCK_IN_EVICTION). + */ + + KEYCACHE_DBUG_PRINT("find_key_block", + ("request for old page in block %u " + "wrmode: %d block->status: %d", + BLOCK_NUMBER(block), wrmode, block->status)); + /* + Only reading requests can proceed until the old dirty page is flushed, + all others are to be suspended, then resubmitted + */ + if (!wrmode && !(block->status & BLOCK_REASSIGNED)) + { + /* + This is a read request and the block not yet reassigned. We can + register our request and proceed. This unlinks the block from + the LRU ring and protects it against eviction. + */ + reg_requests(keycache, block, 1); + } + else + { + /* + Either this is a write request for a block that is in eviction + or in free. We must not use it any more. Instead we must evict + another block. But we cannot do this before the eviction/free is + done. Otherwise we would find the same hash_link + block again + and again. + + Or this is a read request for a block in eviction/free that does + not require a flush, but waits for readers to finish with the + block. We do not read this block to let the eviction/free happen + as soon as possible. Again we must wait so that we don't find + the same hash_link + block again and again. + */ + DBUG_ASSERT(hash_link->requests); + hash_link->requests--; + KEYCACHE_DBUG_PRINT("find_key_block", + ("request waiting for old page to be saved")); + wait_on_queue(&block->wqueue[COND_FOR_SAVED], &keycache->cache_lock); + KEYCACHE_DBUG_PRINT("find_key_block", + ("request for old page resubmitted")); + /* + The block is no longer assigned to this hash_link. + Get another one. + */ + goto restart; + } + } + else + { + /* + This is a request for a new block or for a block not to be removed. + Either + - block == NULL or + - block not assigned to this hash_link or + - block assigned but not yet read from file, + or + - block assigned with valid (changed or unchanged) data and + - it will not be reassigned/freed. + */ + if (! block) + { + /* No block is assigned to the hash_link yet. */ + if (keycache->blocks_unused) + { + if (keycache->free_block_list) + { + /* There is a block in the free list. */ + block= keycache->free_block_list; + keycache->free_block_list= block->next_used; + block->next_used= NULL; + } + else + { + size_t block_mem_offset; + /* There are some never used blocks, take first of them */ + DBUG_ASSERT(keycache->blocks_used < + (ulong) keycache->disk_blocks); + block= &keycache->block_root[keycache->blocks_used]; + block_mem_offset= + ((size_t) keycache->blocks_used) * keycache->key_cache_block_size; + block->buffer= ADD_TO_PTR(keycache->block_mem, + block_mem_offset, + uchar*); + keycache->blocks_used++; + DBUG_ASSERT(!block->next_used); + } + DBUG_ASSERT(!block->prev_used); + DBUG_ASSERT(!block->next_changed); + DBUG_ASSERT(!block->prev_changed); + DBUG_ASSERT(!block->hash_link); + DBUG_ASSERT(!block->status); + DBUG_ASSERT(!block->requests); + keycache->blocks_unused--; + block->status= BLOCK_IN_USE; + block->length= 0; + block->offset= keycache->key_cache_block_size; + block->requests= 1; + block->temperature= BLOCK_COLD; + block->hits_left= init_hits_left; + block->last_hit_time= 0; + block->hash_link= hash_link; + hash_link->block= block; + link_to_file_list(keycache, block, file, 0); + page_status= PAGE_TO_BE_READ; + KEYCACHE_DBUG_PRINT("find_key_block", + ("got free or never used block %u", + BLOCK_NUMBER(block))); + } + else + { + /* + There are no free blocks and no never used blocks, use a block + from the LRU ring. + */ + + if (! keycache->used_last) + { + /* + The LRU ring is empty. Wait until a new block is added to + it. Several threads might wait here for the same hash_link, + all of them must get the same block. While waiting for a + block, after a block is selected for this hash_link, other + threads can run first before this one awakes. During this + time interval other threads find this hash_link pointing to + the block, which is still assigned to another hash_link. In + this case the block is not marked BLOCK_IN_SWITCH yet, but + it is marked BLOCK_IN_EVICTION. + */ + + struct st_my_thread_var *thread= my_thread_var; + thread->keycache_link= (void *) hash_link; + link_into_queue(&keycache->waiting_for_block, thread); + do + { + KEYCACHE_DBUG_PRINT("find_key_block: wait", + ("suspend thread %ld", (ulong) thread->id)); + keycache_pthread_cond_wait(&thread->suspend, + &keycache->cache_lock); + } + while (thread->next); + thread->keycache_link= NULL; + /* Assert that block has a request registered. */ + DBUG_ASSERT(hash_link->block->requests); + /* Assert that block is not in LRU ring. */ + DBUG_ASSERT(!hash_link->block->next_used); + DBUG_ASSERT(!hash_link->block->prev_used); + } + /* + If we waited above, hash_link->block has been assigned by + link_block(). Otherwise it is still NULL. In the latter case + we need to grab a block from the LRU ring ourselves. + */ + block= hash_link->block; + if (! block) + { + /* Select the last block from the LRU ring. */ + block= keycache->used_last->next_used; + block->hits_left= init_hits_left; + block->last_hit_time= 0; + hash_link->block= block; + /* + Register a request on the block. This unlinks it from the + LRU ring and protects it against eviction. + */ + DBUG_ASSERT(!block->requests); + reg_requests(keycache, block,1); + /* + We do not need to set block->status|= BLOCK_IN_EVICTION here + because we will set block->status|= BLOCK_IN_SWITCH + immediately without releasing the lock in between. This does + also support debugging. When looking at the block, one can + see if the block has been selected by link_block() after the + LRU ring was empty, or if it was grabbed directly from the + LRU ring in this branch. + */ + } + + /* + If we had to wait above, there is a small chance that another + thread grabbed this block for the same file block already. But + in most cases the first condition is true. + */ + if (block->hash_link != hash_link && + ! (block->status & BLOCK_IN_SWITCH) ) + { + /* this is a primary request for a new page */ + block->status|= BLOCK_IN_SWITCH; + + KEYCACHE_DBUG_PRINT("find_key_block", + ("got block %u for new page", BLOCK_NUMBER(block))); + + if (block->status & BLOCK_CHANGED) + { + /* The block contains a dirty page - push it out of the cache */ + + KEYCACHE_DBUG_PRINT("find_key_block", ("block is dirty")); + if (block->status & BLOCK_IN_FLUSH) + { + /* + The block is marked for flush. If we do not wait here, + it could happen that we write the block, reassign it to + another file block, then, before the new owner can read + the new file block, the flusher writes the cache block + (which still has the old contents) to the new file block! + */ + wait_on_queue(&block->wqueue[COND_FOR_SAVED], + &keycache->cache_lock); + /* + The block is marked BLOCK_IN_SWITCH. It should be left + alone except for reading. No free, no write. + */ + DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); + DBUG_ASSERT(!(block->status & (BLOCK_REASSIGNED | + BLOCK_CHANGED | + BLOCK_FOR_UPDATE))); + } + else + { + block->status|= BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE; + /* + BLOCK_IN_EVICTION may be true or not. Other flags must + have a fixed value. + */ + DBUG_ASSERT((block->status & ~BLOCK_IN_EVICTION) == + (BLOCK_READ | BLOCK_IN_SWITCH | + BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE | + BLOCK_CHANGED | BLOCK_IN_USE)); + DBUG_ASSERT(block->hash_link); + + keycache_pthread_mutex_unlock(&keycache->cache_lock); + /* + The call is thread safe because only the current + thread might change the block->hash_link value + */ + error= (int)my_pwrite(block->hash_link->file, + block->buffer + block->offset, + block->length - block->offset, + block->hash_link->diskpos + block->offset, + MYF(MY_NABP | MY_WAIT_IF_FULL)); + keycache_pthread_mutex_lock(&keycache->cache_lock); + + /* Block status must not have changed. */ + DBUG_ASSERT((block->status & ~BLOCK_IN_EVICTION) == + (BLOCK_READ | BLOCK_IN_SWITCH | + BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE | + BLOCK_CHANGED | BLOCK_IN_USE) || fail_block(block)); + keycache->global_cache_write++; + } + } + + block->status|= BLOCK_REASSIGNED; + /* + The block comes from the LRU ring. It must have a hash_link + assigned. + */ + DBUG_ASSERT(block->hash_link); + if (block->hash_link) + { + /* + All pending requests for this page must be resubmitted. + This must be done before waiting for readers. They could + wait for the flush to complete. And we must also do it + after the wait. Flushers might try to free the block while + we wait. They would wait until the reassignment is + complete. Also the block status must reflect the correct + situation: The block is not changed nor in flush any more. + Note that we must not change the BLOCK_CHANGED flag + outside of link_to_file_list() so that it is always in the + correct queue and the *blocks_changed counters are + correct. + */ + block->status&= ~(BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE); + link_to_file_list(keycache, block, block->hash_link->file, 1); + release_whole_queue(&block->wqueue[COND_FOR_SAVED]); + /* + The block is still assigned to its old hash_link. + Wait until all pending read requests + for this page are executed + (we could have avoided this waiting, if we had read + a page in the cache in a sweep, without yielding control) + */ + wait_for_readers(keycache, block); + DBUG_ASSERT(block->hash_link && block->hash_link->block == block && + block->prev_changed); + /* The reader must not have been a writer. */ + DBUG_ASSERT(!(block->status & BLOCK_CHANGED)); + + /* Wake flushers that might have found the block in between. */ + release_whole_queue(&block->wqueue[COND_FOR_SAVED]); + + /* Remove the hash link for the old file block from the hash. */ + unlink_hash(keycache, block->hash_link); + + /* + For sanity checks link_to_file_list() asserts that block + and hash_link refer to each other. Hence we need to assign + the hash_link first, but then we would not know if it was + linked before. Hence we would not know if to unlink it. So + unlink it here and call link_to_file_list(..., FALSE). + */ + unlink_changed(block); + } + block->status= error ? BLOCK_ERROR : BLOCK_IN_USE ; + block->length= 0; + block->offset= keycache->key_cache_block_size; + block->hash_link= hash_link; + link_to_file_list(keycache, block, file, 0); + page_status= PAGE_TO_BE_READ; + + KEYCACHE_DBUG_ASSERT(block->hash_link->block == block); + KEYCACHE_DBUG_ASSERT(hash_link->block->hash_link == hash_link); + } + else + { + /* + Either (block->hash_link == hash_link), + or (block->status & BLOCK_IN_SWITCH). + + This is for secondary requests for a new file block only. + Either it is already assigned to the new hash_link meanwhile + (if we had to wait due to empty LRU), or it is already in + eviction by another thread. Since this block has been + grabbed from the LRU ring and attached to this hash_link, + another thread cannot grab the same block from the LRU ring + anymore. If the block is in eviction already, it must become + attached to the same hash_link and as such destined for the + same file block. + */ + KEYCACHE_DBUG_PRINT("find_key_block", + ("block->hash_link: %p hash_link: %p " + "block->status: %u", block->hash_link, + hash_link, block->status )); + page_status= (((block->hash_link == hash_link) && + (block->status & BLOCK_READ)) ? + PAGE_READ : PAGE_WAIT_TO_BE_READ); + } + } + } + else + { + /* + Block is not NULL. This hash_link points to a block. + Either + - block not assigned to this hash_link (yet) or + - block assigned but not yet read from file, + or + - block assigned with valid (changed or unchanged) data and + - it will not be reassigned/freed. + + The first condition means hash_link points to a block in + eviction. This is not necessarily marked by BLOCK_IN_SWITCH yet. + But then it is marked BLOCK_IN_EVICTION. See the NOTE in + link_block(). In both cases it is destined for this hash_link + and its file block address. When this hash_link got its block + address, the block was removed from the LRU ring and cannot be + selected for eviction (for another hash_link) again. + + Register a request on the block. This is another protection + against eviction. + */ + DBUG_ASSERT(((block->hash_link != hash_link) && + (block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))) || + ((block->hash_link == hash_link) && + !(block->status & BLOCK_READ)) || + ((block->status & BLOCK_READ) && + !(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH)))); + reg_requests(keycache, block, 1); + KEYCACHE_DBUG_PRINT("find_key_block", + ("block->hash_link: %p hash_link: %p " + "block->status: %u", block->hash_link, + hash_link, block->status )); + page_status= (((block->hash_link == hash_link) && + (block->status & BLOCK_READ)) ? + PAGE_READ : PAGE_WAIT_TO_BE_READ); + } + } + + KEYCACHE_DBUG_ASSERT(page_status != -1); + /* Same assert basically, but be very sure. */ + KEYCACHE_DBUG_ASSERT(block); + /* Assert that block has a request and is not in LRU ring. */ + DBUG_ASSERT(block->requests); + DBUG_ASSERT(!block->next_used); + DBUG_ASSERT(!block->prev_used); + /* Assert that we return the correct block. */ + DBUG_ASSERT((page_status == PAGE_WAIT_TO_BE_READ) || + ((block->hash_link->file == file) && + (block->hash_link->diskpos == filepos))); + *page_st=page_status; + KEYCACHE_DBUG_PRINT("find_key_block", + ("fd: %d pos: %lu block->status: %u page_status: %d", + file, (ulong) filepos, block->status, + page_status)); + +#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG) + DBUG_EXECUTE("check_keycache2", + test_key_cache(keycache, "end of find_key_block",0);); +#endif + KEYCACHE_THREAD_TRACE("find_key_block:end"); + DBUG_RETURN(block); +} + + +/* + Read into a key cache block buffer from disk. + + SYNOPSIS + + read_block_{primary|secondary}() + keycache pointer to a key cache data structure + block block to which buffer the data is to be read + read_length size of data to be read + min_length at least so much data must be read + + RETURN VALUE + None + + NOTES. + The function either reads a page data from file to the block buffer, + or waits until another thread reads it. What page to read is determined + by a block parameter - reference to a hash link for this page. + If an error occurs THE BLOCK_ERROR bit is set in the block status. + We do not report error when the size of successfully read + portion is less than read_length, but not less than min_length. +*/ + +static void read_block_primary(SIMPLE_KEY_CACHE_CB *keycache, + BLOCK_LINK *block, uint read_length, + uint min_length) +{ + size_t got_length; + + /* On entry cache_lock is locked */ + + KEYCACHE_THREAD_TRACE("read_block_primary"); + + /* + This code is executed only by threads that submitted primary + requests. Until block->status contains BLOCK_READ, all other + request for the block become secondary requests. For a primary + request the block must be properly initialized. + */ + DBUG_ASSERT(((block->status & ~BLOCK_FOR_UPDATE) == BLOCK_IN_USE) || + fail_block(block)); + DBUG_ASSERT((block->length == 0) || fail_block(block)); + DBUG_ASSERT((block->offset == keycache->key_cache_block_size) || + fail_block(block)); + DBUG_ASSERT((block->requests > 0) || fail_block(block)); + + KEYCACHE_DBUG_PRINT("read_block_primary", + ("page to be read by primary request")); + + keycache->global_cache_read++; + /* Page is not in buffer yet, is to be read from disk */ + keycache_pthread_mutex_unlock(&keycache->cache_lock); + /* + Here other threads may step in and register as secondary readers. + They will register in block->wqueue[COND_FOR_REQUESTED]. + */ + got_length= my_pread(block->hash_link->file, block->buffer, + read_length, block->hash_link->diskpos, MYF(0)); + keycache_pthread_mutex_lock(&keycache->cache_lock); + /* + The block can now have been marked for free (in case of + FLUSH_RELEASE). Otherwise the state must be unchanged. + */ + DBUG_ASSERT(((block->status & ~(BLOCK_REASSIGNED | + BLOCK_FOR_UPDATE)) == BLOCK_IN_USE) || + fail_block(block)); + DBUG_ASSERT((block->length == 0) || fail_block(block)); + DBUG_ASSERT((block->offset == keycache->key_cache_block_size) || + fail_block(block)); + DBUG_ASSERT((block->requests > 0) || fail_block(block)); + + if (got_length < min_length) + block->status|= BLOCK_ERROR; + else + { + block->status|= BLOCK_READ; + block->length= (uint)got_length; + /* + Do not set block->offset here. If this block is marked + BLOCK_CHANGED later, we want to flush only the modified part. So + only a writer may set block->offset down from + keycache->key_cache_block_size. + */ + } + KEYCACHE_DBUG_PRINT("read_block_primary", + ("primary request: new page in cache")); + /* Signal that all pending requests for this page now can be processed */ + release_whole_queue(&block->wqueue[COND_FOR_REQUESTED]); + + DBUG_ASSERT(keycache->can_be_used); +} + + +static void read_block_secondary(SIMPLE_KEY_CACHE_CB *keycache, + BLOCK_LINK *block) +{ + KEYCACHE_THREAD_TRACE("read_block_secondary"); + + /* + This code is executed only by threads that submitted secondary + requests. At this point it could happen that the cache block is + not yet assigned to the hash_link for the requested file block. + But at awake from the wait this should be the case. Unfortunately + we cannot assert this here because we do not know the hash_link + for the requested file block nor the file and position. So we have + to assert this in the caller. + */ + KEYCACHE_DBUG_PRINT("read_block_secondary", + ("secondary request waiting for new page to be read")); + + wait_on_queue(&block->wqueue[COND_FOR_REQUESTED], &keycache->cache_lock); + + KEYCACHE_DBUG_PRINT("read_block_secondary", + ("secondary request: new page in cache")); + + DBUG_ASSERT(keycache->can_be_used); + DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); +} + + +/* + Read a block of data from a simple key cache into a buffer + + SYNOPSIS + + simple_key_cache_read() + keycache pointer to the control block of a simple key cache + file handler for the file for the block of data to be read + filepos position of the block of data in the file + level determines the weight of the data + buff buffer to where the data must be placed + length length of the buffer + block_length length of the read data from a key cache block + return_buffer return pointer to the key cache buffer with the data + + DESCRIPTION + This function is the implementation of the key_cache_read interface + function that is employed by simple (non-partitioned) key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type SIMPLE_KEY_CACHE_CB for a simple key + cache. + In a general case the function reads a block of data from the key cache + into the buffer buff of the size specified by the parameter length. The + beginning of the block of data to be read is specified by the parameters + file and filepos. The length of the read data is the same as the length + of the buffer. The data is read into the buffer in key_cache_block_size + increments. If the next portion of the data is not found in any key cache + block, first it is read from file into the key cache. + If the parameter return_buffer is not ignored and its value is TRUE, and + the data to be read of the specified size block_length can be read from one + key cache buffer, then the function returns a pointer to the data in the + key cache buffer. + The function takse into account parameters block_length and return buffer + only in a single-threaded environment. + The parameter 'level' is used only by the midpoint insertion strategy + when the data or its portion cannot be found in the key cache. + + RETURN VALUE + Returns address from where the data is placed if successful, 0 - otherwise. + + NOTES + Filepos must be a multiple of 'block_length', but it doesn't + have to be a multiple of key_cache_block_size; +*/ + +uchar *simple_key_cache_read(SIMPLE_KEY_CACHE_CB *keycache, + File file, my_off_t filepos, int level, + uchar *buff, uint length, + uint block_length __attribute__((unused)), + int return_buffer __attribute__((unused))) +{ + my_bool locked_and_incremented= FALSE; + int error=0; + uchar *start= buff; + DBUG_ENTER("simple_key_cache_read"); + DBUG_PRINT("enter", ("fd: %u pos: %lu length: %u", + (uint) file, (ulong) filepos, length)); + + if (keycache->key_cache_inited) + { + /* Key cache is used */ + reg1 BLOCK_LINK *block; + uint read_length; + uint offset; + int page_st; + + if (MYSQL_KEYCACHE_READ_START_ENABLED()) + { + MYSQL_KEYCACHE_READ_START(my_filename(file), length, + (ulong) (keycache->blocks_used * + keycache->key_cache_block_size), + (ulong) (keycache->blocks_unused * + keycache->key_cache_block_size)); + } + + /* + When the key cache is once initialized, we use the cache_lock to + reliably distinguish the cases of normal operation, resizing, and + disabled cache. We always increment and decrement + 'cnt_for_resize_op' so that a resizer can wait for pending I/O. + */ + keycache_pthread_mutex_lock(&keycache->cache_lock); + /* + Cache resizing has two phases: Flushing and re-initializing. In + the flush phase read requests are allowed to bypass the cache for + blocks not in the cache. find_key_block() returns NULL in this + case. + + After the flush phase new I/O requests must wait until the + re-initialization is done. The re-initialization can be done only + if no I/O request is in progress. The reason is that + key_cache_block_size can change. With enabled cache, I/O is done + in chunks of key_cache_block_size. Every chunk tries to use a + cache block first. If the block size changes in the middle, a + block could be missed and old data could be read. + */ + while (keycache->in_resize && !keycache->resize_in_flush) + wait_on_queue(&keycache->resize_queue, &keycache->cache_lock); + /* Register the I/O for the next resize. */ + inc_counter_for_resize_op(keycache); + locked_and_incremented= TRUE; + /* Requested data may not always be aligned to cache blocks. */ + offset= (uint) (filepos % keycache->key_cache_block_size); + /* Read data in key_cache_block_size increments */ + do + { + /* Cache could be disabled in a later iteration. */ + if (!keycache->can_be_used) + { + KEYCACHE_DBUG_PRINT("key_cache_read", ("keycache cannot be used")); + goto no_key_cache; + } + /* Start reading at the beginning of the cache block. */ + filepos-= offset; + /* Do not read beyond the end of the cache block. */ + read_length= length; + set_if_smaller(read_length, keycache->key_cache_block_size-offset); + KEYCACHE_DBUG_ASSERT(read_length > 0); + + /* Request the cache block that matches file/pos. */ + keycache->global_cache_r_requests++; + + MYSQL_KEYCACHE_READ_BLOCK(keycache->key_cache_block_size); + + block=find_key_block(keycache, file, filepos, level, 0, &page_st); + if (!block) + { + /* + This happens only for requests submitted during key cache + resize. The block is not in the cache and shall not go in. + Read directly from file. + */ + keycache->global_cache_read++; + keycache_pthread_mutex_unlock(&keycache->cache_lock); + error= (my_pread(file, (uchar*) buff, read_length, + filepos + offset, MYF(MY_NABP)) != 0); + keycache_pthread_mutex_lock(&keycache->cache_lock); + goto next_block; + } + if (!(block->status & BLOCK_ERROR)) + { + if (page_st == PAGE_TO_BE_READ) + { + MYSQL_KEYCACHE_READ_MISS(); + read_block_primary(keycache, block, + keycache->key_cache_block_size, read_length+offset); + } + else if (page_st == PAGE_WAIT_TO_BE_READ) + { + MYSQL_KEYCACHE_READ_MISS(); + /* The requested page is to be read into the block buffer */ + read_block_secondary(keycache, block); + + /* + A secondary request must now have the block assigned to the + requested file block. + */ + DBUG_ASSERT(block->hash_link->file == file); + DBUG_ASSERT(block->hash_link->diskpos == filepos); + } + else if (block->length < read_length + offset) + { + /* + Impossible if nothing goes wrong: + this could only happen if we are using a file with + small key blocks and are trying to read outside the file + */ + my_errno= -1; + block->status|= BLOCK_ERROR; + } + else + { + MYSQL_KEYCACHE_READ_HIT(); + } + } + + /* block status may have added BLOCK_ERROR in the above 'if'. */ + if (!(block->status & BLOCK_ERROR)) + { + { + DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); +#if !defined(SERIALIZED_READ_FROM_CACHE) + keycache_pthread_mutex_unlock(&keycache->cache_lock); +#endif + + /* Copy data from the cache buffer */ + memcpy(buff, block->buffer+offset, (size_t) read_length); + +#if !defined(SERIALIZED_READ_FROM_CACHE) + keycache_pthread_mutex_lock(&keycache->cache_lock); + DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); +#endif + } + } + + remove_reader(block); + + /* Error injection for coverage testing. */ + DBUG_EXECUTE_IF("key_cache_read_block_error", + block->status|= BLOCK_ERROR;); + + /* Do not link erroneous blocks into the LRU ring, but free them. */ + if (!(block->status & BLOCK_ERROR)) + { + /* + Link the block into the LRU ring if it's the last submitted + request for the block. This enables eviction for the block. + */ + unreg_request(keycache, block, 1); + } + else + { + free_block(keycache, block); + error= 1; + break; + } + + next_block: + buff+= read_length; + filepos+= read_length+offset; + offset= 0; + + } while ((length-= read_length)); + if (MYSQL_KEYCACHE_READ_DONE_ENABLED()) + { + MYSQL_KEYCACHE_READ_DONE((ulong) (keycache->blocks_used * + keycache->key_cache_block_size), + (ulong) (keycache->blocks_unused * + keycache->key_cache_block_size)); + } + goto end; + } + KEYCACHE_DBUG_PRINT("key_cache_read", ("keycache not initialized")); + +no_key_cache: + /* Key cache is not used */ + + keycache->global_cache_r_requests++; + keycache->global_cache_read++; + + if (locked_and_incremented) + keycache_pthread_mutex_unlock(&keycache->cache_lock); + if (my_pread(file, (uchar*) buff, length, filepos, MYF(MY_NABP))) + error= 1; + if (locked_and_incremented) + keycache_pthread_mutex_lock(&keycache->cache_lock); + +end: + if (locked_and_incremented) + { + dec_counter_for_resize_op(keycache); + keycache_pthread_mutex_unlock(&keycache->cache_lock); + } + DBUG_PRINT("exit", ("error: %d", error )); + DBUG_RETURN(error ? (uchar*) 0 : start); +} + + +/* + Insert a block of file data from a buffer into a simple key cache + + SYNOPSIS + simple_key_cache_insert() + keycache pointer to the control block of a simple key cache + file handler for the file to insert data from + filepos position of the block of data in the file to insert + level determines the weight of the data + buff buffer to read data from + length length of the data in the buffer + + DESCRIPTION + This function is the implementation of the key_cache_insert interface + function that is employed by simple (non-partitioned) key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type SIMPLE_KEY_CACHE_CB for a simple key + cache. + The function writes a block of file data from a buffer into the key cache. + The buffer is specified with the parameters buff and length - the pointer + to the beginning of the buffer and its size respectively. It's assumed + the buffer contains the data from 'file' allocated from the position + filepos. The data is copied from the buffer in key_cache_block_size + increments. + The parameter level is used to set one characteristic for the key buffers + loaded with the data from buff. The characteristic is used only by the + midpoint insertion strategy. + + RETURN VALUE + 0 if a success, 1 - otherwise. + + NOTES + The function is used by MyISAM to move all blocks from a index file to + the key cache. It can be performed in parallel with reading the file data + from the key buffers by other threads. + +*/ + +static +int simple_key_cache_insert(SIMPLE_KEY_CACHE_CB *keycache, + File file, my_off_t filepos, int level, + uchar *buff, uint length) +{ + int error= 0; + DBUG_ENTER("key_cache_insert"); + DBUG_PRINT("enter", ("fd: %u pos: %lu length: %u", + (uint) file,(ulong) filepos, length)); + + if (keycache->key_cache_inited) + { + /* Key cache is used */ + reg1 BLOCK_LINK *block; + uint read_length; + uint offset; + int page_st; + my_bool locked_and_incremented= FALSE; + + /* + When the keycache is once initialized, we use the cache_lock to + reliably distinguish the cases of normal operation, resizing, and + disabled cache. We always increment and decrement + 'cnt_for_resize_op' so that a resizer can wait for pending I/O. + */ + keycache_pthread_mutex_lock(&keycache->cache_lock); + /* + We do not load index data into a disabled cache nor into an + ongoing resize. + */ + if (!keycache->can_be_used || keycache->in_resize) + goto no_key_cache; + /* Register the pseudo I/O for the next resize. */ + inc_counter_for_resize_op(keycache); + locked_and_incremented= TRUE; + /* Loaded data may not always be aligned to cache blocks. */ + offset= (uint) (filepos % keycache->key_cache_block_size); + /* Load data in key_cache_block_size increments. */ + do + { + /* Cache could be disabled or resizing in a later iteration. */ + if (!keycache->can_be_used || keycache->in_resize) + goto no_key_cache; + /* Start loading at the beginning of the cache block. */ + filepos-= offset; + /* Do not load beyond the end of the cache block. */ + read_length= length; + set_if_smaller(read_length, keycache->key_cache_block_size-offset); + KEYCACHE_DBUG_ASSERT(read_length > 0); + + /* The block has been read by the caller already. */ + keycache->global_cache_read++; + /* Request the cache block that matches file/pos. */ + keycache->global_cache_r_requests++; + block= find_key_block(keycache, file, filepos, level, 0, &page_st); + if (!block) + { + /* + This happens only for requests submitted during key cache + resize. The block is not in the cache and shall not go in. + Stop loading index data. + */ + goto no_key_cache; + } + if (!(block->status & BLOCK_ERROR)) + { + if (page_st == PAGE_WAIT_TO_BE_READ) + { + /* + this is a secondary request for a block to be read into the + cache. The block is in eviction. It is not yet assigned to + the requested file block (It does not point to the right + hash_link). So we cannot call remove_reader() on the block. + And we cannot access the hash_link directly here. We need to + wait until the assignment is complete. read_block_secondary() + executes the correct wait. + */ + read_block_secondary(keycache, block); + + /* + A secondary request must now have the block assigned to the + requested file block. + */ + DBUG_ASSERT(block->hash_link->file == file); + DBUG_ASSERT(block->hash_link->diskpos == filepos); + } + else if (page_st == PAGE_TO_BE_READ && + (offset || (read_length < keycache->key_cache_block_size))) + { + /* + this is a primary request for a block to be read into the + cache and the supplied data does not fill the whole block. + + This function is called on behalf of a LOAD INDEX INTO CACHE + statement, which is a read-only task and allows other + readers. It is possible that a parallel running reader tries + to access this block. If it needs more data than has been + supplied here, it would report an error. To be sure that we + have all data in the block that is available in the file, we + read the block ourselves. + + Though reading again what the caller did read already is an + expensive operation, we need to do this for correctness. + */ + read_block_primary(keycache, block, keycache->key_cache_block_size, + read_length + offset); + } + else if (page_st == PAGE_TO_BE_READ) + { + /* + This is a new block in the cache. If we come here, we have + data for the whole block. + */ + DBUG_ASSERT(block->hash_link->requests); + DBUG_ASSERT(block->status & BLOCK_IN_USE); + DBUG_ASSERT((page_st == PAGE_TO_BE_READ) || + (block->status & BLOCK_READ)); + +#if !defined(SERIALIZED_READ_FROM_CACHE) + keycache_pthread_mutex_unlock(&keycache->cache_lock); + /* + Here other threads may step in and register as secondary readers. + They will register in block->wqueue[COND_FOR_REQUESTED]. + */ +#endif + + /* Copy data from buff */ + memcpy(block->buffer+offset, buff, (size_t) read_length); + +#if !defined(SERIALIZED_READ_FROM_CACHE) + keycache_pthread_mutex_lock(&keycache->cache_lock); + DBUG_ASSERT(block->status & BLOCK_IN_USE); + DBUG_ASSERT((page_st == PAGE_TO_BE_READ) || + (block->status & BLOCK_READ)); +#endif + /* + After the data is in the buffer, we can declare the block + valid. Now other threads do not need to register as + secondary readers any more. They can immediately access the + block. + */ + block->status|= BLOCK_READ; + block->length= read_length+offset; + /* + Do not set block->offset here. If this block is marked + BLOCK_CHANGED later, we want to flush only the modified part. So + only a writer may set block->offset down from + keycache->key_cache_block_size. + */ + KEYCACHE_DBUG_PRINT("key_cache_insert", + ("primary request: new page in cache")); + /* Signal all pending requests. */ + release_whole_queue(&block->wqueue[COND_FOR_REQUESTED]); + } + else + { + /* + page_st == PAGE_READ. The block is in the buffer. All data + must already be present. Blocks are always read with all + data available on file. Assert that the block does not have + less contents than the preloader supplies. If the caller has + data beyond block->length, it means that a file write has + been done while this block was in cache and not extended + with the new data. If the condition is met, we can simply + ignore the block. + */ + DBUG_ASSERT((page_st == PAGE_READ) && + (read_length + offset <= block->length)); + } + + /* + A secondary request must now have the block assigned to the + requested file block. It does not hurt to check it for primary + requests too. + */ + DBUG_ASSERT(block->hash_link->file == file); + DBUG_ASSERT(block->hash_link->diskpos == filepos); + DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); + } /* end of if (!(block->status & BLOCK_ERROR)) */ + + remove_reader(block); + + /* Error injection for coverage testing. */ + DBUG_EXECUTE_IF("key_cache_insert_block_error", + block->status|= BLOCK_ERROR; errno=EIO;); + + /* Do not link erroneous blocks into the LRU ring, but free them. */ + if (!(block->status & BLOCK_ERROR)) + { + /* + Link the block into the LRU ring if it's the last submitted + request for the block. This enables eviction for the block. + */ + unreg_request(keycache, block, 1); + } + else + { + free_block(keycache, block); + error= 1; + break; + } + + buff+= read_length; + filepos+= read_length+offset; + offset= 0; + + } while ((length-= read_length)); + + no_key_cache: + if (locked_and_incremented) + dec_counter_for_resize_op(keycache); + keycache_pthread_mutex_unlock(&keycache->cache_lock); + } + DBUG_RETURN(error); +} + + +/* + Write a buffer into a simple key cache + + SYNOPSIS + + simple_key_cache_write() + keycache pointer to the control block of a simple key cache + file handler for the file to write data to + file_extra maps of key cache partitions containing + dirty pages from file + filepos position in the file to write data to + level determines the weight of the data + buff buffer with the data + length length of the buffer + dont_write if is 0 then all dirty pages involved in writing + should have been flushed from key cache + + DESCRIPTION + This function is the implementation of the key_cache_write interface + function that is employed by simple (non-partitioned) key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type SIMPLE_KEY_CACHE_CB for a simple key + cache. + In a general case the function copies data from a buffer into the key + cache. The buffer is specified with the parameters buff and length - + the pointer to the beginning of the buffer and its size respectively. + It's assumed the buffer contains the data to be written into 'file' + starting from the position filepos. The data is copied from the buffer + in key_cache_block_size increments. + If the value of the parameter dont_write is FALSE then the function + also writes the data into file. + The parameter level is used to set one characteristic for the key buffers + filled with the data from buff. The characteristic is employed only by + the midpoint insertion strategy. + The parameter file_extra currently makes sense only for simple key caches + that are elements of a partitioned key cache. It provides a pointer to the + shared bitmap of the partitions that may contains dirty pages for the file. + This bitmap is used to optimize the function + flush_partitioned_key_cache_blocks. + + RETURN VALUE + 0 if a success, 1 - otherwise. + + NOTES + This implementation exploits the fact that the function is called only + when a thread has got an exclusive lock for the key file. +*/ + +static +int simple_key_cache_write(SIMPLE_KEY_CACHE_CB *keycache, + File file, void *file_extra __attribute__((unused)), + my_off_t filepos, int level, + uchar *buff, uint length, + uint block_length __attribute__((unused)), + int dont_write) +{ + my_bool locked_and_incremented= FALSE; + int error=0; + DBUG_ENTER("simple_key_cache_write"); + DBUG_PRINT("enter", + ("fd: %u pos: %lu length: %u block_length: %u" + " key_block_length: %u", + (uint) file, (ulong) filepos, length, block_length, + keycache ? keycache->key_cache_block_size : 0)); + + if (!dont_write) + { + /* purecov: begin inspected */ + /* Not used in the server. */ + /* Force writing from buff into disk. */ + keycache->global_cache_w_requests++; + keycache->global_cache_write++; + if (my_pwrite(file, buff, length, filepos, MYF(MY_NABP | MY_WAIT_IF_FULL))) + DBUG_RETURN(1); + /* purecov: end */ + } + +#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG) + DBUG_EXECUTE("check_keycache", + test_key_cache(keycache, "start of key_cache_write", 1);); +#endif + + if (keycache->key_cache_inited) + { + /* Key cache is used */ + reg1 BLOCK_LINK *block; + uint read_length; + uint offset; + int page_st; + + if (MYSQL_KEYCACHE_WRITE_START_ENABLED()) + { + MYSQL_KEYCACHE_WRITE_START(my_filename(file), length, + (ulong) (keycache->blocks_used * + keycache->key_cache_block_size), + (ulong) (keycache->blocks_unused * + keycache->key_cache_block_size)); + } + + /* + When the key cache is once initialized, we use the cache_lock to + reliably distinguish the cases of normal operation, resizing, and + disabled cache. We always increment and decrement + 'cnt_for_resize_op' so that a resizer can wait for pending I/O. + */ + keycache_pthread_mutex_lock(&keycache->cache_lock); + /* + Cache resizing has two phases: Flushing and re-initializing. In + the flush phase write requests can modify dirty blocks that are + not yet in flush. Otherwise they are allowed to bypass the cache. + find_key_block() returns NULL in both cases (clean blocks and + non-cached blocks). + + After the flush phase new I/O requests must wait until the + re-initialization is done. The re-initialization can be done only + if no I/O request is in progress. The reason is that + key_cache_block_size can change. With enabled cache I/O is done in + chunks of key_cache_block_size. Every chunk tries to use a cache + block first. If the block size changes in the middle, a block + could be missed and data could be written below a cached block. + */ + while (keycache->in_resize && !keycache->resize_in_flush) + wait_on_queue(&keycache->resize_queue, &keycache->cache_lock); + /* Register the I/O for the next resize. */ + inc_counter_for_resize_op(keycache); + locked_and_incremented= TRUE; + /* Requested data may not always be aligned to cache blocks. */ + offset= (uint) (filepos % keycache->key_cache_block_size); + /* Write data in key_cache_block_size increments. */ + do + { + /* Cache could be disabled in a later iteration. */ + if (!keycache->can_be_used) + goto no_key_cache; + + MYSQL_KEYCACHE_WRITE_BLOCK(keycache->key_cache_block_size); + /* Start writing at the beginning of the cache block. */ + filepos-= offset; + /* Do not write beyond the end of the cache block. */ + read_length= length; + set_if_smaller(read_length, keycache->key_cache_block_size-offset); + KEYCACHE_DBUG_ASSERT(read_length > 0); + + /* Request the cache block that matches file/pos. */ + keycache->global_cache_w_requests++; + block= find_key_block(keycache, file, filepos, level, 1, &page_st); + if (!block) + { + /* + This happens only for requests submitted during key cache + resize. The block is not in the cache and shall not go in. + Write directly to file. + */ + if (dont_write) + { + /* Used in the server. */ + keycache->global_cache_write++; + keycache_pthread_mutex_unlock(&keycache->cache_lock); + if (my_pwrite(file, (uchar*) buff, read_length, filepos + offset, + MYF(MY_NABP | MY_WAIT_IF_FULL))) + error=1; + keycache_pthread_mutex_lock(&keycache->cache_lock); + } + goto next_block; + } + /* + Prevent block from flushing and from being selected for to be + freed. This must be set when we release the cache_lock. + However, we must not set the status of the block before it is + assigned to this file/pos. + */ + if (page_st != PAGE_WAIT_TO_BE_READ) + block->status|= BLOCK_FOR_UPDATE; + /* + We must read the file block first if it is not yet in the cache + and we do not replace all of its contents. + + In cases where the cache block is big enough to contain (parts + of) index blocks of different indexes, our request can be + secondary (PAGE_WAIT_TO_BE_READ). In this case another thread is + reading the file block. If the read completes after us, it + overwrites our new contents with the old contents. So we have to + wait for the other thread to complete the read of this block. + read_block_primary|secondary() takes care for the wait. + */ + if (!(block->status & BLOCK_ERROR)) + { + if (page_st == PAGE_TO_BE_READ && + (offset || read_length < keycache->key_cache_block_size)) + { + read_block_primary(keycache, block, + offset + read_length >= keycache->key_cache_block_size? + offset : keycache->key_cache_block_size, + offset); + /* + Prevent block from flushing and from being selected for to be + freed. This must be set when we release the cache_lock. + Here we set it in case we could not set it above. + */ + block->status|= BLOCK_FOR_UPDATE; + } + else if (page_st == PAGE_WAIT_TO_BE_READ) + { + read_block_secondary(keycache, block); + block->status|= BLOCK_FOR_UPDATE; + } + } + /* + The block should always be assigned to the requested file block + here. It need not be BLOCK_READ when overwriting the whole block. + */ + DBUG_ASSERT(block->hash_link->file == file); + DBUG_ASSERT(block->hash_link->diskpos == filepos); + DBUG_ASSERT(block->status & BLOCK_IN_USE); + DBUG_ASSERT((page_st == PAGE_TO_BE_READ) || (block->status & BLOCK_READ)); + /* + The block to be written must not be marked BLOCK_REASSIGNED. + Otherwise it could be freed in dirty state or reused without + another flush during eviction. It must also not be in flush. + Otherwise the old contens may have been flushed already and + the flusher could clear BLOCK_CHANGED without flushing the + new changes again. + */ + DBUG_ASSERT(!(block->status & BLOCK_REASSIGNED)); + + while (block->status & BLOCK_IN_FLUSHWRITE) + { + /* + Another thread is flushing the block. It was dirty already. + Wait until the block is flushed to file. Otherwise we could + modify the buffer contents just while it is written to file. + An unpredictable file block contents would be the result. + While we wait, several things can happen to the block, + including another flush. But the block cannot be reassigned to + another hash_link until we release our request on it. + */ + wait_on_queue(&block->wqueue[COND_FOR_SAVED], &keycache->cache_lock); + DBUG_ASSERT(keycache->can_be_used); + DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); + /* Still must not be marked for free. */ + DBUG_ASSERT(!(block->status & BLOCK_REASSIGNED)); + DBUG_ASSERT(block->hash_link && (block->hash_link->block == block)); + } + + /* + We could perhaps release the cache_lock during access of the + data like in the other functions. Locks outside of the key cache + assure that readers and a writer do not access the same range of + data. Parallel accesses should happen only if the cache block + contains multiple index block(fragment)s. So different parts of + the buffer would be read/written. An attempt to flush during + memcpy() is prevented with BLOCK_FOR_UPDATE. + */ + if (!(block->status & BLOCK_ERROR)) + { +#if !defined(SERIALIZED_READ_FROM_CACHE) + keycache_pthread_mutex_unlock(&keycache->cache_lock); +#endif + memcpy(block->buffer+offset, buff, (size_t) read_length); + +#if !defined(SERIALIZED_READ_FROM_CACHE) + keycache_pthread_mutex_lock(&keycache->cache_lock); +#endif + } + + if (!dont_write) + { + /* Not used in the server. buff has been written to disk at start. */ + if ((block->status & BLOCK_CHANGED) && + (!offset && read_length >= keycache->key_cache_block_size)) + link_to_file_list(keycache, block, block->hash_link->file, 1); + } + else if (! (block->status & BLOCK_CHANGED)) + link_to_changed_list(keycache, block); + block->status|=BLOCK_READ; + /* + Allow block to be selected for to be freed. Since it is marked + BLOCK_CHANGED too, it won't be selected for to be freed without + a flush. + */ + block->status&= ~BLOCK_FOR_UPDATE; + set_if_smaller(block->offset, offset); + set_if_bigger(block->length, read_length+offset); + + /* Threads may be waiting for the changes to be complete. */ + release_whole_queue(&block->wqueue[COND_FOR_REQUESTED]); + + /* + If only a part of the cache block is to be replaced, and the + rest has been read from file, then the cache lock has been + released for I/O and it could be possible that another thread + wants to evict or free the block and waits for it to be + released. So we must not just decrement hash_link->requests, but + also wake a waiting thread. + */ + remove_reader(block); + + /* Error injection for coverage testing. */ + DBUG_EXECUTE_IF("key_cache_write_block_error", + block->status|= BLOCK_ERROR;); + + /* Do not link erroneous blocks into the LRU ring, but free them. */ + if (!(block->status & BLOCK_ERROR)) + { + /* + Link the block into the LRU ring if it's the last submitted + request for the block. This enables eviction for the block. + */ + unreg_request(keycache, block, 1); + } + else + { + /* Pretend a "clean" block to avoid complications. */ + block->status&= ~(BLOCK_CHANGED); + free_block(keycache, block); + error= 1; + break; + } + + next_block: + buff+= read_length; + filepos+= read_length+offset; + offset= 0; + + } while ((length-= read_length)); + goto end; + } + +no_key_cache: + /* Key cache is not used */ + if (dont_write) + { + /* Used in the server. */ + keycache->global_cache_w_requests++; + keycache->global_cache_write++; + if (locked_and_incremented) + keycache_pthread_mutex_unlock(&keycache->cache_lock); + if (my_pwrite(file, (uchar*) buff, length, filepos, + MYF(MY_NABP | MY_WAIT_IF_FULL))) + error=1; + if (locked_and_incremented) + keycache_pthread_mutex_lock(&keycache->cache_lock); + } + +end: + if (locked_and_incremented) + { + dec_counter_for_resize_op(keycache); + keycache_pthread_mutex_unlock(&keycache->cache_lock); + } + + if (MYSQL_KEYCACHE_WRITE_DONE_ENABLED()) + { + MYSQL_KEYCACHE_WRITE_DONE((ulong) (keycache->blocks_used * + keycache->key_cache_block_size), + (ulong) (keycache->blocks_unused * + keycache->key_cache_block_size)); + } + +#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG) + DBUG_EXECUTE("exec", + test_key_cache(keycache, "end of key_cache_write", 1);); +#endif + DBUG_RETURN(error); +} + + +/* + Free block. + + SYNOPSIS + free_block() + keycache Pointer to a key cache data structure + block Pointer to the block to free + + DESCRIPTION + Remove reference to block from hash table. + Remove block from the chain of clean blocks. + Add block to the free list. + + NOTE + Block must not be free (status == 0). + Block must not be in free_block_list. + Block must not be in the LRU ring. + Block must not be in eviction (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH). + Block must not be in free (BLOCK_REASSIGNED). + Block must not be in flush (BLOCK_IN_FLUSH). + Block must not be dirty (BLOCK_CHANGED). + Block must not be in changed_blocks (dirty) hash. + Block must be in file_blocks (clean) hash. + Block must refer to a hash_link. + Block must have a request registered on it. +*/ + +static void free_block(SIMPLE_KEY_CACHE_CB *keycache, BLOCK_LINK *block) +{ + KEYCACHE_THREAD_TRACE("free block"); + KEYCACHE_DBUG_PRINT("free_block", + ("block %u to be freed, hash_link %p status: %u", + BLOCK_NUMBER(block), block->hash_link, + block->status)); + /* + Assert that the block is not free already. And that it is in a clean + state. Note that the block might just be assigned to a hash_link and + not yet read (BLOCK_READ may not be set here). In this case a reader + is registered in the hash_link and free_block() will wait for it + below. + */ + DBUG_ASSERT((block->status & BLOCK_IN_USE) && + !(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | + BLOCK_REASSIGNED | BLOCK_IN_FLUSH | + BLOCK_CHANGED | BLOCK_FOR_UPDATE))); + /* Assert that the block is in a file_blocks chain. */ + DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); + /* Assert that the block is not in the LRU ring. */ + DBUG_ASSERT(!block->next_used && !block->prev_used); + /* + IMHO the below condition (if()) makes no sense. I can't see how it + could be possible that free_block() is entered with a NULL hash_link + pointer. The only place where it can become NULL is in free_block() + (or before its first use ever, but for those blocks free_block() is + not called). I don't remove the conditional as it cannot harm, but + place an DBUG_ASSERT to confirm my hypothesis. Eventually the + condition (if()) can be removed. + */ + DBUG_ASSERT(block->hash_link && block->hash_link->block == block); + if (block->hash_link) + { + /* + While waiting for readers to finish, new readers might request the + block. But since we set block->status|= BLOCK_REASSIGNED, they + will wait on block->wqueue[COND_FOR_SAVED]. They must be signalled + later. + */ + block->status|= BLOCK_REASSIGNED; + wait_for_readers(keycache, block); + /* + The block must not have been freed by another thread. Repeat some + checks. An additional requirement is that it must be read now + (BLOCK_READ). + */ + DBUG_ASSERT(block->hash_link && block->hash_link->block == block); + DBUG_ASSERT((block->status & (BLOCK_READ | BLOCK_IN_USE | + BLOCK_REASSIGNED)) && + !(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | + BLOCK_IN_FLUSH | BLOCK_CHANGED | + BLOCK_FOR_UPDATE))); + DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); + DBUG_ASSERT(!block->prev_used); + /* + Unset BLOCK_REASSIGNED again. If we hand the block to an evicting + thread (through unreg_request() below), other threads must not see + this flag. They could become confused. + */ + block->status&= ~BLOCK_REASSIGNED; + /* + Do not release the hash_link until the block is off all lists. + At least not if we hand it over for eviction in unreg_request(). + */ + } + + /* + Unregister the block request and link the block into the LRU ring. + This enables eviction for the block. If the LRU ring was empty and + threads are waiting for a block, then the block wil be handed over + for eviction immediately. Otherwise we will unlink it from the LRU + ring again, without releasing the lock in between. So decrementing + the request counter and updating statistics are the only relevant + operation in this case. Assert that there are no other requests + registered. + */ + DBUG_ASSERT(block->requests == 1); + unreg_request(keycache, block, 0); + /* + Note that even without releasing the cache lock it is possible that + the block is immediately selected for eviction by link_block() and + thus not added to the LRU ring. In this case we must not touch the + block any more. + */ + if (block->status & BLOCK_IN_EVICTION) + return; + + /* Error blocks are not put into the LRU ring. */ + if (!(block->status & BLOCK_ERROR)) + { + /* Here the block must be in the LRU ring. Unlink it again. */ + DBUG_ASSERT(block->next_used && block->prev_used && + *block->prev_used == block); + unlink_block(keycache, block); + } + if (block->temperature == BLOCK_WARM) + keycache->warm_blocks--; + block->temperature= BLOCK_COLD; + + /* Remove from file_blocks hash. */ + unlink_changed(block); + + /* Remove reference to block from hash table. */ + unlink_hash(keycache, block->hash_link); + block->hash_link= NULL; + + block->status= 0; + block->length= 0; + block->offset= keycache->key_cache_block_size; + KEYCACHE_THREAD_TRACE("free block"); + KEYCACHE_DBUG_PRINT("free_block", ("block is freed")); + + /* Enforced by unlink_changed(), but just to be sure. */ + DBUG_ASSERT(!block->next_changed && !block->prev_changed); + /* Enforced by unlink_block(): not in LRU ring nor in free_block_list. */ + DBUG_ASSERT(!block->next_used && !block->prev_used); + /* Insert the free block in the free list. */ + block->next_used= keycache->free_block_list; + keycache->free_block_list= block; + /* Keep track of the number of currently unused blocks. */ + keycache->blocks_unused++; + + /* All pending requests for this page must be resubmitted. */ + release_whole_queue(&block->wqueue[COND_FOR_SAVED]); +} + + +static int cmp_sec_link(BLOCK_LINK **a, BLOCK_LINK **b) +{ + return (((*a)->hash_link->diskpos < (*b)->hash_link->diskpos) ? -1 : + ((*a)->hash_link->diskpos > (*b)->hash_link->diskpos) ? 1 : 0); +} + + +/* + Flush a portion of changed blocks to disk, + free used blocks if requested +*/ + +static int flush_cached_blocks(SIMPLE_KEY_CACHE_CB *keycache, + File file, BLOCK_LINK **cache, + BLOCK_LINK **end, + enum flush_type type) +{ + int error; + int last_errno= 0; + uint count= (uint) (end-cache); + + /* Don't lock the cache during the flush */ + keycache_pthread_mutex_unlock(&keycache->cache_lock); + /* + As all blocks referred in 'cache' are marked by BLOCK_IN_FLUSH + we are guarunteed no thread will change them + */ + my_qsort((uchar*) cache, count, sizeof(*cache), (qsort_cmp) cmp_sec_link); + + keycache_pthread_mutex_lock(&keycache->cache_lock); + /* + Note: Do not break the loop. We have registered a request on every + block in 'cache'. These must be unregistered by free_block() or + unreg_request(). + */ + for ( ; cache != end ; cache++) + { + BLOCK_LINK *block= *cache; + + KEYCACHE_DBUG_PRINT("flush_cached_blocks", + ("block %u to be flushed", BLOCK_NUMBER(block))); + /* + If the block contents is going to be changed, we abandon the flush + for this block. flush_key_blocks_int() will restart its search and + handle the block properly. + */ + if (!(block->status & BLOCK_FOR_UPDATE)) + { + /* Blocks coming here must have a certain status. */ + DBUG_ASSERT(block->hash_link); + DBUG_ASSERT(block->hash_link->block == block); + DBUG_ASSERT(block->hash_link->file == file); + DBUG_ASSERT((block->status & ~BLOCK_IN_EVICTION) == + (BLOCK_READ | BLOCK_IN_FLUSH | BLOCK_CHANGED | BLOCK_IN_USE)); + block->status|= BLOCK_IN_FLUSHWRITE; + keycache_pthread_mutex_unlock(&keycache->cache_lock); + error= (int)my_pwrite(file, block->buffer + block->offset, + block->length - block->offset, + block->hash_link->diskpos + block->offset, + MYF(MY_NABP | MY_WAIT_IF_FULL)); + keycache_pthread_mutex_lock(&keycache->cache_lock); + keycache->global_cache_write++; + if (error) + { + block->status|= BLOCK_ERROR; + if (!last_errno) + last_errno= errno ? errno : -1; + } + block->status&= ~BLOCK_IN_FLUSHWRITE; + /* Block must not have changed status except BLOCK_FOR_UPDATE. */ + DBUG_ASSERT(block->hash_link); + DBUG_ASSERT(block->hash_link->block == block); + DBUG_ASSERT(block->hash_link->file == file); + DBUG_ASSERT((block->status & ~(BLOCK_FOR_UPDATE | BLOCK_IN_EVICTION)) == + (BLOCK_READ | BLOCK_IN_FLUSH | BLOCK_CHANGED | BLOCK_IN_USE)); + /* + Set correct status and link in right queue for free or later use. + free_block() must not see BLOCK_CHANGED and it may need to wait + for readers of the block. These should not see the block in the + wrong hash. If not freeing the block, we need to have it in the + right queue anyway. + */ + link_to_file_list(keycache, block, file, 1); + } + block->status&= ~BLOCK_IN_FLUSH; + /* + Let to proceed for possible waiting requests to write to the block page. + It might happen only during an operation to resize the key cache. + */ + release_whole_queue(&block->wqueue[COND_FOR_SAVED]); + /* type will never be FLUSH_IGNORE_CHANGED here */ + if (!(type == FLUSH_KEEP || type == FLUSH_FORCE_WRITE) && + !(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | + BLOCK_FOR_UPDATE))) + { + /* + Note that a request has been registered against the block in + flush_key_blocks_int(). + */ + free_block(keycache, block); + } + else + { + /* + Link the block into the LRU ring if it's the last submitted + request for the block. This enables eviction for the block. + Note that a request has been registered against the block in + flush_key_blocks_int(). + */ + unreg_request(keycache, block, 1); + } + + } /* end of for ( ; cache != end ; cache++) */ + return last_errno; +} + + +/* + Flush all key blocks for a file to disk, but don't do any mutex locks + + SYNOPSIS + flush_key_blocks_int() + keycache pointer to a key cache data structure + file handler for the file to flush to + flush_type type of the flush + + NOTES + This function doesn't do any mutex locks because it needs to be called both + from flush_key_blocks and flush_all_key_blocks (the later one does the + mutex lock in the resize_key_cache() function). + + We do only care about changed blocks that exist when the function is + entered. We do not guarantee that all changed blocks of the file are + flushed if more blocks change while this function is running. + + RETURN + 0 ok + 1 error +*/ + +static int flush_key_blocks_int(SIMPLE_KEY_CACHE_CB *keycache, + File file, enum flush_type type) +{ + BLOCK_LINK *cache_buff[FLUSH_CACHE],**cache; + int last_errno= 0; + int last_errcnt= 0; + DBUG_ENTER("flush_key_blocks_int"); + DBUG_PRINT("enter",("file: %d blocks_used: %lu blocks_changed: %lu", + file, keycache->blocks_used, keycache->blocks_changed)); + +#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG) + DBUG_EXECUTE("check_keycache", + test_key_cache(keycache, "start of flush_key_blocks", 0);); +#endif + + DBUG_ASSERT(type != FLUSH_KEEP_LAZY); + cache= cache_buff; + if (keycache->disk_blocks > 0 && + (!my_disable_flush_key_blocks || type != FLUSH_KEEP)) + { + /* Key cache exists and flush is not disabled */ + int error= 0; + uint count= FLUSH_CACHE; + BLOCK_LINK **pos,**end; + BLOCK_LINK *first_in_switch= NULL; + BLOCK_LINK *last_in_flush; + BLOCK_LINK *last_for_update; + BLOCK_LINK *block, *next; +#if defined(KEYCACHE_DEBUG) + uint cnt=0; +#endif + + if (type != FLUSH_IGNORE_CHANGED) + { + /* + Count how many key blocks we have to cache to be able + to flush all dirty pages with minimum seek moves + */ + count= 0; + for (block= keycache->changed_blocks[FILE_HASH(file, keycache)] ; + block ; + block= block->next_changed) + { + if ((block->hash_link->file == file) && + !(block->status & BLOCK_IN_FLUSH)) + { + count++; + KEYCACHE_DBUG_ASSERT(count<= keycache->blocks_used); + } + } + /* + Allocate a new buffer only if its bigger than the one we have. + Assure that we always have some entries for the case that new + changed blocks appear while we need to wait for something. + */ + if ((count > FLUSH_CACHE) && + !(cache= (BLOCK_LINK**) my_malloc(key_memory_KEY_CACHE, + sizeof(BLOCK_LINK*)*count, MYF(0)))) + cache= cache_buff; + /* + After a restart there could be more changed blocks than now. + So we should not let count become smaller than the fixed buffer. + */ + if (cache == cache_buff) + count= FLUSH_CACHE; + } + + /* Retrieve the blocks and write them to a buffer to be flushed */ +restart: + last_in_flush= NULL; + last_for_update= NULL; + end= (pos= cache)+count; + for (block= keycache->changed_blocks[FILE_HASH(file, keycache)] ; + block ; + block= next) + { +#if defined(KEYCACHE_DEBUG) + cnt++; + KEYCACHE_DBUG_ASSERT(cnt <= keycache->blocks_used); +#endif + next= block->next_changed; + if (block->hash_link->file == file) + { + if (!(block->status & (BLOCK_IN_FLUSH | BLOCK_FOR_UPDATE))) + { + /* + Note: The special handling of BLOCK_IN_SWITCH is obsolete + since we set BLOCK_IN_FLUSH if the eviction includes a + flush. It can be removed in a later version. + */ + if (!(block->status & BLOCK_IN_SWITCH)) + { + /* + We care only for the blocks for which flushing was not + initiated by another thread and which are not in eviction. + Registering a request on the block unlinks it from the LRU + ring and protects against eviction. + */ + reg_requests(keycache, block, 1); + if (type != FLUSH_IGNORE_CHANGED) + { + /* It's not a temporary file */ + if (pos == end) + { + /* + This should happen relatively seldom. Remove the + request because we won't do anything with the block + but restart and pick it again in the next iteration. + */ + unreg_request(keycache, block, 0); + /* + This happens only if there is not enough + memory for the big block + */ + if ((error= flush_cached_blocks(keycache, file, cache, + end,type))) + { + /* Do not loop infinitely trying to flush in vain. */ + if ((last_errno == error) && (++last_errcnt > 5)) + goto err; + last_errno= error; + } + /* + Restart the scan as some other thread might have changed + the changed blocks chain: the blocks that were in switch + state before the flush started have to be excluded + */ + goto restart; + } + /* + Mark the block with BLOCK_IN_FLUSH in order not to let + other threads to use it for new pages and interfere with + our sequence of flushing dirty file pages. We must not + set this flag before actually putting the block on the + write burst array called 'cache'. + */ + block->status|= BLOCK_IN_FLUSH; + /* Add block to the array for a write burst. */ + *pos++= block; + } + else + { + /* It's a temporary file */ + DBUG_ASSERT(!(block->status & BLOCK_REASSIGNED)); + /* + free_block() must not be called with BLOCK_CHANGED. Note + that we must not change the BLOCK_CHANGED flag outside of + link_to_file_list() so that it is always in the correct + queue and the *blocks_changed counters are correct. + */ + link_to_file_list(keycache, block, file, 1); + if (!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))) + { + /* A request has been registered against the block above. */ + free_block(keycache, block); + } + else + { + /* + Link the block into the LRU ring if it's the last + submitted request for the block. This enables eviction + for the block. A request has been registered against + the block above. + */ + unreg_request(keycache, block, 1); + } + } + } + else + { + /* + Link the block into a list of blocks 'in switch'. + + WARNING: Here we introduce a place where a changed block + is not in the changed_blocks hash! This is acceptable for + a BLOCK_IN_SWITCH. Never try this for another situation. + Other parts of the key cache code rely on changed blocks + being in the changed_blocks hash. + */ + unlink_changed(block); + link_changed(block, &first_in_switch); + } + } + else if (type != FLUSH_KEEP) + { + /* + During the normal flush at end of statement (FLUSH_KEEP) we + do not need to ensure that blocks in flush or update by + other threads are flushed. They will be flushed by them + later. In all other cases we must assure that we do not have + any changed block of this file in the cache when this + function returns. + */ + if (block->status & BLOCK_IN_FLUSH) + { + /* Remember the last block found to be in flush. */ + last_in_flush= block; + } + else + { + /* Remember the last block found to be selected for update. */ + last_for_update= block; + } + } + } + } + if (pos != cache) + { + if ((error= flush_cached_blocks(keycache, file, cache, pos, type))) + { + /* Do not loop inifnitely trying to flush in vain. */ + if ((last_errno == error) && (++last_errcnt > 5)) + goto err; + last_errno= error; + } + /* + Do not restart here during the normal flush at end of statement + (FLUSH_KEEP). We have now flushed at least all blocks that were + changed when entering this function. In all other cases we must + assure that we do not have any changed block of this file in the + cache when this function returns. + */ + if (type != FLUSH_KEEP) + goto restart; + } + if (last_in_flush) + { + /* + There are no blocks to be flushed by this thread, but blocks in + flush by other threads. Wait until one of the blocks is flushed. + Re-check the condition for last_in_flush. We may have unlocked + the cache_lock in flush_cached_blocks(). The state of the block + could have changed. + */ + if (last_in_flush->status & BLOCK_IN_FLUSH) + wait_on_queue(&last_in_flush->wqueue[COND_FOR_SAVED], + &keycache->cache_lock); + /* Be sure not to lose a block. They may be flushed in random order. */ + goto restart; + } + if (last_for_update) + { + /* + There are no blocks to be flushed by this thread, but blocks for + update by other threads. Wait until one of the blocks is updated. + Re-check the condition for last_for_update. We may have unlocked + the cache_lock in flush_cached_blocks(). The state of the block + could have changed. + */ + if (last_for_update->status & BLOCK_FOR_UPDATE) + wait_on_queue(&last_for_update->wqueue[COND_FOR_REQUESTED], + &keycache->cache_lock); + /* The block is now changed. Flush it. */ + goto restart; + } + + /* + Wait until the list of blocks in switch is empty. The threads that + are switching these blocks will relink them to clean file chains + while we wait and thus empty the 'first_in_switch' chain. + */ + while (first_in_switch) + { +#if defined(KEYCACHE_DEBUG) + cnt= 0; +#endif + wait_on_queue(&first_in_switch->wqueue[COND_FOR_SAVED], + &keycache->cache_lock); +#if defined(KEYCACHE_DEBUG) + cnt++; + KEYCACHE_DBUG_ASSERT(cnt <= keycache->blocks_used); +#endif + /* + Do not restart here. We have flushed all blocks that were + changed when entering this function and were not marked for + eviction. Other threads have now flushed all remaining blocks in + the course of their eviction. + */ + } + + if (! (type == FLUSH_KEEP || type == FLUSH_FORCE_WRITE)) + { + BLOCK_LINK *last_in_switch= NULL; + uint total_found= 0; + uint found; + last_for_update= NULL; + + /* + Finally free all clean blocks for this file. + During resize this may be run by two threads in parallel. + */ + do + { + found= 0; + for (block= keycache->file_blocks[FILE_HASH(file, keycache)] ; + block ; + block= next) + { + /* Remember the next block. After freeing we cannot get at it. */ + next= block->next_changed; + + /* Changed blocks cannot appear in the file_blocks hash. */ + DBUG_ASSERT(!(block->status & BLOCK_CHANGED)); + if (block->hash_link->file == file) + { + /* We must skip blocks that will be changed. */ + if (block->status & BLOCK_FOR_UPDATE) + { + last_for_update= block; + continue; + } + + /* + We must not free blocks in eviction (BLOCK_IN_EVICTION | + BLOCK_IN_SWITCH) or blocks intended to be freed + (BLOCK_REASSIGNED). + */ + if (!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | + BLOCK_REASSIGNED))) + { + struct st_hash_link *UNINIT_VAR(next_hash_link); + my_off_t UNINIT_VAR(next_diskpos); + File UNINIT_VAR(next_file); + uint UNINIT_VAR(next_status); + uint UNINIT_VAR(hash_requests); + + total_found++; + found++; + KEYCACHE_DBUG_ASSERT(found <= keycache->blocks_used); + + /* + Register a request. This unlinks the block from the LRU + ring and protects it against eviction. This is required + by free_block(). + */ + reg_requests(keycache, block, 1); + + /* + free_block() may need to wait for readers of the block. + This is the moment where the other thread can move the + 'next' block from the chain. free_block() needs to wait + if there are requests for the block pending. + */ + if (next && (hash_requests= block->hash_link->requests)) + { + /* Copy values from the 'next' block and its hash_link. */ + next_status= next->status; + next_hash_link= next->hash_link; + next_diskpos= next_hash_link->diskpos; + next_file= next_hash_link->file; + DBUG_ASSERT(next == next_hash_link->block); + } + + free_block(keycache, block); + /* + If we had to wait and the state of the 'next' block + changed, break the inner loop. 'next' may no longer be + part of the current chain. + + We do not want to break the loop after every free_block(), + not even only after waits. The chain might be quite long + and contain blocks for many files. Traversing it again and + again to find more blocks for this file could become quite + inefficient. + */ + if (next && hash_requests && + ((next_status != next->status) || + (next_hash_link != next->hash_link) || + (next_file != next_hash_link->file) || + (next_diskpos != next_hash_link->diskpos) || + (next != next_hash_link->block))) + break; + } + else + { + last_in_switch= block; + } + } + } /* end for block in file_blocks */ + } while (found); + + /* + If any clean block has been found, we may have waited for it to + become free. In this case it could be possible that another clean + block became dirty. This is possible if the write request existed + before the flush started (BLOCK_FOR_UPDATE). Re-check the hashes. + */ + if (total_found) + goto restart; + + /* + To avoid an infinite loop, wait until one of the blocks marked + for update is updated. + */ + if (last_for_update) + { + /* We did not wait. Block must not have changed status. */ + DBUG_ASSERT(last_for_update->status & BLOCK_FOR_UPDATE); + wait_on_queue(&last_for_update->wqueue[COND_FOR_REQUESTED], + &keycache->cache_lock); + goto restart; + } + + /* + To avoid an infinite loop wait until one of the blocks marked + for eviction is switched. + */ + if (last_in_switch) + { + /* We did not wait. Block must not have changed status. */ + DBUG_ASSERT(last_in_switch->status & (BLOCK_IN_EVICTION | + BLOCK_IN_SWITCH | + BLOCK_REASSIGNED)); + wait_on_queue(&last_in_switch->wqueue[COND_FOR_SAVED], + &keycache->cache_lock); + goto restart; + } + + } /* if (! (type == FLUSH_KEEP || type == FLUSH_FORCE_WRITE)) */ + + } /* if (keycache->disk_blocks > 0 */ + + DBUG_EXECUTE("check_keycache", + test_key_cache(keycache, "end of flush_key_blocks", 0);); +err: + if (cache != cache_buff) + my_free(cache); + if (last_errno) + errno=last_errno; /* Return first error */ + DBUG_RETURN(last_errno != 0); +} + + +/* + Flush all blocks for a file from key buffers of a simple key cache + + SYNOPSIS + + flush_simple_key_blocks() + keycache pointer to the control block of a simple key cache + file handler for the file to flush to + file_extra maps of key cache partitions containing + dirty pages from file (not used) + flush_type type of the flush operation + + DESCRIPTION + This function is the implementation of the flush_key_blocks interface + function that is employed by simple (non-partitioned) key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type S_KEY_CACHE_CB for a simple key + cache. + In a general case the function flushes the data from all dirty key + buffers related to the file 'file' into this file. The function does + exactly this if the value of the parameter type is FLUSH_KEEP. If the + value of this parameter is FLUSH_RELEASE, the function additionally + releases the key buffers containing data from 'file' for new usage. + If the value of the parameter type is FLUSH_IGNORE_CHANGED the function + just releases the key buffers containing data from 'file'. + The parameter file_extra currently is not used by this function. + + RETURN + 0 ok + 1 error + + NOTES + This implementation exploits the fact that the function is called only + when a thread has got an exclusive lock for the key file. +*/ + +static +int flush_simple_key_cache_blocks(SIMPLE_KEY_CACHE_CB *keycache, + File file, + void *file_extra __attribute__((unused)), + enum flush_type type) +{ + int res= 0; + DBUG_ENTER("flush_key_blocks"); + DBUG_PRINT("enter", ("keycache: %p", keycache)); + + if (!keycache->key_cache_inited) + DBUG_RETURN(0); + + keycache_pthread_mutex_lock(&keycache->cache_lock); + /* While waiting for lock, keycache could have been ended. */ + if (keycache->disk_blocks > 0) + { + inc_counter_for_resize_op(keycache); + res= flush_key_blocks_int(keycache, file, type); + dec_counter_for_resize_op(keycache); + } + keycache_pthread_mutex_unlock(&keycache->cache_lock); + DBUG_RETURN(res); +} + + +/* + Flush all blocks in the key cache to disk. + + SYNOPSIS + flush_all_key_blocks() + keycache pointer to key cache root structure + + DESCRIPTION + + Flushing of the whole key cache is done in two phases. + + 1. Flush all changed blocks, waiting for them if necessary. Loop + until there is no changed block left in the cache. + + 2. Free all clean blocks. Normally this means free all blocks. The + changed blocks were flushed in phase 1 and became clean. However we + may need to wait for blocks that are read by other threads. While we + wait, a clean block could become changed if that operation started + before the resize operation started. To be safe we must restart at + phase 1. + + When we can run through the changed_blocks and file_blocks hashes + without finding a block any more, then we are done. + + Note that we hold keycache->cache_lock all the time unless we need + to wait for something. + + RETURN + 0 OK + != 0 Error +*/ + +static int flush_all_key_blocks(SIMPLE_KEY_CACHE_CB *keycache) +{ + BLOCK_LINK *block; + uint total_found; + uint found; + uint idx; + uint changed_blocks_hash_size= keycache->changed_blocks_hash_size; + DBUG_ENTER("flush_all_key_blocks"); + + do + { + mysql_mutex_assert_owner(&keycache->cache_lock); + total_found= 0; + + /* + Phase1: Flush all changed blocks, waiting for them if necessary. + Loop until there is no changed block left in the cache. + */ + do + { + found= 0; + /* Step over the whole changed_blocks hash array. */ + for (idx= 0; idx < changed_blocks_hash_size; idx++) + { + /* + If an array element is non-empty, use the first block from its + chain to find a file for flush. All changed blocks for this + file are flushed. So the same block will not appear at this + place again with the next iteration. New writes for blocks are + not accepted during the flush. If multiple files share the + same hash bucket, one of them will be flushed per iteration + of the outer loop of phase 1. + */ + while ((block= keycache->changed_blocks[idx])) + { + found++; + /* + Flush dirty blocks but do not free them yet. They can be used + for reading until all other blocks are flushed too. + */ + if (flush_key_blocks_int(keycache, block->hash_link->file, + FLUSH_FORCE_WRITE)) + DBUG_RETURN(1); + } + } + } while (found); + + /* + Phase 2: Free all clean blocks. Normally this means free all + blocks. The changed blocks were flushed in phase 1 and became + clean. However we may need to wait for blocks that are read by + other threads. While we wait, a clean block could become changed + if that operation started before the resize operation started. To + be safe we must restart at phase 1. + */ + do + { + found= 0; + /* Step over the whole file_blocks hash array. */ + for (idx= 0; idx < changed_blocks_hash_size; idx++) + { + /* + If an array element is non-empty, use the first block from its + chain to find a file for flush. All blocks for this file are + freed. So the same block will not appear at this place again + with the next iteration. If multiple files share the + same hash bucket, one of them will be flushed per iteration + of the outer loop of phase 2. + */ + while ((block= keycache->file_blocks[idx])) + { + total_found++; + found++; + if (flush_key_blocks_int(keycache, block->hash_link->file, + FLUSH_RELEASE)) + DBUG_RETURN(1); + } + } + } while (found); + + /* + If any clean block has been found, we may have waited for it to + become free. In this case it could be possible that another clean + block became dirty. This is possible if the write request existed + before the resize started (BLOCK_FOR_UPDATE). Re-check the hashes. + */ + } while (total_found); + +#ifndef DBUG_OFF + /* Now there should not exist any block any more. */ + for (idx= 0; idx < changed_blocks_hash_size; idx++) + { + DBUG_ASSERT(!keycache->changed_blocks[idx]); + DBUG_ASSERT(!keycache->file_blocks[idx]); + } +#endif + + DBUG_RETURN(0); +} + + +/* + Reset the counters of a simple key cache + + SYNOPSIS + reset_simple_key_cache_counters() + name the name of a key cache + keycache pointer to the control block of a simple key cache + + DESCRIPTION + This function is the implementation of the reset_key_cache_counters + interface function that is employed by simple (non-partitioned) key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type S_KEY_CACHE_CB for a simple key cache. + This function resets the values of all statistical counters for the key + cache to 0. + The parameter name is currently not used. + + RETURN + 0 on success (always because it can't fail) +*/ + +static +int reset_simple_key_cache_counters(const char *name __attribute__((unused)), + SIMPLE_KEY_CACHE_CB *keycache) +{ + DBUG_ENTER("reset_simple_key_cache_counters"); + if (!keycache->key_cache_inited) + { + DBUG_PRINT("info", ("Key cache %s not initialized.", name)); + DBUG_RETURN(0); + } + DBUG_PRINT("info", ("Resetting counters for key cache %s.", name)); + + keycache->global_blocks_changed= 0; /* Key_blocks_not_flushed */ + keycache->global_cache_r_requests= 0; /* Key_read_requests */ + keycache->global_cache_read= 0; /* Key_reads */ + keycache->global_cache_w_requests= 0; /* Key_write_requests */ + keycache->global_cache_write= 0; /* Key_writes */ + DBUG_RETURN(0); +} + + +#ifndef DBUG_OFF +/* + Test if disk-cache is ok +*/ +static +void test_key_cache(SIMPLE_KEY_CACHE_CB *keycache __attribute__((unused)), + const char *where __attribute__((unused)), + my_bool lock __attribute__((unused))) +{ + /* TODO */ +} +#endif + +#if defined(KEYCACHE_TIMEOUT) + +#define KEYCACHE_DUMP_FILE "keycache_dump.txt" +#define MAX_QUEUE_LEN 100 + + +static void keycache_dump(SIMPLE_KEY_CACHE_CB *keycache) +{ + FILE *keycache_dump_file=fopen(KEYCACHE_DUMP_FILE, "w"); + struct st_my_thread_var *last; + struct st_my_thread_var *thread; + BLOCK_LINK *block; + HASH_LINK *hash_link; + KEYCACHE_PAGE *page; + uint i; + + fprintf(keycache_dump_file, "thread:%lu\n", (ulong) thread->id); + + i=0; + thread=last=waiting_for_hash_link.last_thread; + fprintf(keycache_dump_file, "queue of threads waiting for hash link\n"); + if (thread) + do + { + thread=thread->next; + page= (KEYCACHE_PAGE *) thread->keycache_link; + fprintf(keycache_dump_file, + "thread:%lu, (file,filepos)=(%u,%lu)\n", + (ulong) thread->id,(uint) page->file,(ulong) page->filepos); + if (++i == MAX_QUEUE_LEN) + break; + } + while (thread != last); + + i=0; + thread=last=waiting_for_block.last_thread; + fprintf(keycache_dump_file, "queue of threads waiting for block\n"); + if (thread) + do + { + thread=thread->next; + hash_link= (HASH_LINK *) thread->keycache_link; + fprintf(keycache_dump_file, + "thread:%lu hash_link:%u (file,filepos)=(%u,%lu)\n", + (ulong) thread->id, (uint) HASH_LINK_NUMBER(hash_link), + (uint) hash_link->file,(ulong) hash_link->diskpos); + if (++i == MAX_QUEUE_LEN) + break; + } + while (thread != last); + + for (i=0 ; i< keycache->blocks_used ; i++) + { + int j; + block= &keycache->block_root[i]; + hash_link= block->hash_link; + fprintf(keycache_dump_file, + "block:%u hash_link:%d status:%x #requests=%u waiting_for_readers:%d\n", + i, (int) (hash_link ? HASH_LINK_NUMBER(hash_link) : -1), + block->status, block->requests, block->condvar ? 1 : 0); + for (j=0 ; j < 2; j++) + { + KEYCACHE_WQUEUE *wqueue=&block->wqueue[j]; + thread= last= wqueue->last_thread; + fprintf(keycache_dump_file, "queue #%d\n", j); + if (thread) + { + do + { + thread=thread->next; + fprintf(keycache_dump_file, + "thread:%lu\n", (ulong) thread->id); + if (++i == MAX_QUEUE_LEN) + break; + } + while (thread != last); + } + } + } + fprintf(keycache_dump_file, "LRU chain:"); + block= keycache= used_last; + if (block) + { + do + { + block= block->next_used; + fprintf(keycache_dump_file, + "block:%u, ", BLOCK_NUMBER(block)); + } + while (block != keycache->used_last); + } + fprintf(keycache_dump_file, "\n"); + + fclose(keycache_dump_file); +} + +#endif /* defined(KEYCACHE_TIMEOUT) */ + +#if defined(KEYCACHE_TIMEOUT) && !defined(_WIN32) + + +static int keycache_pthread_cond_wait(mysql_cond_t *cond, + mysql_mutex_t *mutex) +{ + int rc; + struct timeval now; /* time when we started waiting */ + struct timespec timeout; /* timeout value for the wait function */ + struct timezone tz; +#if defined(KEYCACHE_DEBUG) + int cnt=0; +#endif + + /* Get current time */ + gettimeofday(&now, &tz); + /* Prepare timeout value */ + timeout.tv_sec= now.tv_sec + KEYCACHE_TIMEOUT; + /* + timeval uses microseconds. + timespec uses nanoseconds. + 1 nanosecond = 1000 micro seconds + */ + timeout.tv_nsec= now.tv_usec * 1000; + KEYCACHE_THREAD_TRACE_END("started waiting"); +#if defined(KEYCACHE_DEBUG) + cnt++; + if (cnt % 100 == 0) + fprintf(keycache_debug_log, "waiting...\n"); + fflush(keycache_debug_log); +#endif + rc= mysql_cond_timedwait(cond, mutex, &timeout); + KEYCACHE_THREAD_TRACE_BEGIN("finished waiting"); + if (rc == ETIMEDOUT || rc == ETIME) + { +#if defined(KEYCACHE_DEBUG) + fprintf(keycache_debug_log,"aborted by keycache timeout\n"); + fclose(keycache_debug_log); + abort(); +#endif + keycache_dump(); + } + +#if defined(KEYCACHE_DEBUG) + KEYCACHE_DBUG_ASSERT(rc != ETIMEDOUT); +#else + assert(rc != ETIMEDOUT); +#endif + return rc; +} +#else +#if defined(KEYCACHE_DEBUG) +static int keycache_pthread_cond_wait(mysql_cond_t *cond, + mysql_mutex_t *mutex) +{ + int rc; + KEYCACHE_THREAD_TRACE_END("started waiting"); + rc= mysql_cond_wait(cond, mutex); + KEYCACHE_THREAD_TRACE_BEGIN("finished waiting"); + return rc; +} +#endif +#endif /* defined(KEYCACHE_TIMEOUT) && !defined(_WIN32) */ + +#if defined(KEYCACHE_DEBUG) + + +static int keycache_pthread_mutex_lock(mysql_mutex_t *mutex) +{ + int rc; + rc= mysql_mutex_lock(mutex); + KEYCACHE_THREAD_TRACE_BEGIN(""); + return rc; +} + + +static void keycache_pthread_mutex_unlock(mysql_mutex_t *mutex) +{ + KEYCACHE_THREAD_TRACE_END(""); + mysql_mutex_unlock(mutex); +} + + +static int keycache_pthread_cond_signal(mysql_cond_t *cond) +{ + int rc; + KEYCACHE_THREAD_TRACE("signal"); + rc= mysql_cond_signal(cond); + return rc; +} + + +#if defined(KEYCACHE_DEBUG_LOG) + + +static void keycache_debug_print(const char * fmt,...) +{ + va_list args; + va_start(args,fmt); + if (keycache_debug_log) + { + (void) vfprintf(keycache_debug_log, fmt, args); + (void) fputc('\n',keycache_debug_log); + } + va_end(args); +} +#endif /* defined(KEYCACHE_DEBUG_LOG) */ + +#if defined(KEYCACHE_DEBUG_LOG) + + +void keycache_debug_log_close(void) +{ + if (keycache_debug_log) + fclose(keycache_debug_log); +} +#endif /* defined(KEYCACHE_DEBUG_LOG) */ + +#endif /* defined(KEYCACHE_DEBUG) */ + +#ifdef DBUG_ASSERT_EXISTS +#define F_B_PRT(_f_, _v_) DBUG_PRINT("assert_fail", (_f_, _v_)) + +static int fail_block(BLOCK_LINK *block __attribute__((unused))) +{ +#ifndef DBUG_OFF + F_B_PRT("block->next_used: %p\n", block->next_used); + F_B_PRT("block->prev_used: %p\n", block->prev_used); + F_B_PRT("block->next_changed: %p\n", block->next_changed); + F_B_PRT("block->prev_changed: %p\n", block->prev_changed); + F_B_PRT("block->hash_link: %p\n", block->hash_link); + F_B_PRT("block->status: %u\n", block->status); + F_B_PRT("block->length: %u\n", block->length); + F_B_PRT("block->offset: %u\n", block->offset); + F_B_PRT("block->requests: %u\n", block->requests); + F_B_PRT("block->temperature: %u\n", block->temperature); +#endif + return 0; /* Let the assert fail. */ +} +#endif + +#ifndef DBUG_OFF +static int fail_hlink(HASH_LINK *hlink __attribute__((unused))) +{ + F_B_PRT("hlink->next: %p\n", hlink->next); + F_B_PRT("hlink->prev: %p\n", hlink->prev); + F_B_PRT("hlink->block: %p\n", hlink->block); + F_B_PRT("hlink->diskpos: %lu\n", (ulong) hlink->diskpos); + F_B_PRT("hlink->file: %d\n", hlink->file); + return 0; /* Let the assert fail. */ +} + +static int cache_empty(SIMPLE_KEY_CACHE_CB *keycache) +{ + int errcnt= 0; + int idx; + if (keycache->disk_blocks <= 0) + return 1; + for (idx= 0; idx < keycache->disk_blocks; idx++) + { + BLOCK_LINK *block= keycache->block_root + idx; + if (block->status || block->requests || block->hash_link) + { + fprintf(stderr, "block index: %u\n", idx); + fail_block(block); + errcnt++; + } + } + for (idx= 0; idx < keycache->hash_links; idx++) + { + HASH_LINK *hash_link= keycache->hash_link_root + idx; + if (hash_link->requests || hash_link->block) + { + fprintf(stderr, "hash_link index: %u\n", idx); + fail_hlink(hash_link); + errcnt++; + } + } + if (errcnt) + { + fprintf(stderr, "blocks: %d used: %zu\n", + keycache->disk_blocks, keycache->blocks_used); + fprintf(stderr, "hash_links: %d used: %d\n", + keycache->hash_links, keycache->hash_links_used); + fprintf(stderr, "\n"); + } + return !errcnt; +} +#endif + + +/* + Get statistics for a simple key cache + + SYNOPSIS + get_simple_key_cache_statistics() + keycache pointer to the control block of a simple key cache + partition_no partition number (not used) + key_cache_stats OUT pointer to the structure for the returned statistics + + DESCRIPTION + This function is the implementation of the get_key_cache_statistics + interface function that is employed by simple (non-partitioned) key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type SIMPLE_KEY_CACHE_CB for a simple key + cache. This function returns the statistical data for the key cache. + The parameter partition_no is not used by this function. + + RETURN + none +*/ + +static +void get_simple_key_cache_statistics(SIMPLE_KEY_CACHE_CB *keycache, + uint partition_no __attribute__((unused)), + KEY_CACHE_STATISTICS *keycache_stats) +{ + DBUG_ENTER("simple_get_key_cache_statistics"); + + keycache_stats->mem_size= (longlong) keycache->key_cache_mem_size; + keycache_stats->block_size= (longlong) keycache->key_cache_block_size; + keycache_stats->blocks_used= keycache->blocks_used; + keycache_stats->blocks_unused= keycache->blocks_unused; + keycache_stats->blocks_changed= keycache->global_blocks_changed; + keycache_stats->blocks_warm= keycache->warm_blocks; + keycache_stats->read_requests= keycache->global_cache_r_requests; + keycache_stats->reads= keycache->global_cache_read; + keycache_stats->write_requests= keycache->global_cache_w_requests; + keycache_stats->writes= keycache->global_cache_write; + DBUG_VOID_RETURN; +} + + +/* + The array of pointer to the key cache interface functions used for simple + key caches. Any simple key cache objects including those incorporated into + partitioned keys caches exploit this array. + + The current implementation of these functions allows to call them from + the MySQL server code directly. We don't do it though. +*/ + +static KEY_CACHE_FUNCS simple_key_cache_funcs = +{ + (INIT_KEY_CACHE) init_simple_key_cache, + (RESIZE_KEY_CACHE) resize_simple_key_cache, + (CHANGE_KEY_CACHE_PARAM) change_simple_key_cache_param, + (KEY_CACHE_READ) simple_key_cache_read, + (KEY_CACHE_INSERT) simple_key_cache_insert, + (KEY_CACHE_WRITE) simple_key_cache_write, + (FLUSH_KEY_BLOCKS) flush_simple_key_cache_blocks, + (RESET_KEY_CACHE_COUNTERS) reset_simple_key_cache_counters, + (END_KEY_CACHE) end_simple_key_cache, + (GET_KEY_CACHE_STATISTICS) get_simple_key_cache_statistics, +}; + + +/****************************************************************************** + Partitioned Key Cache Module + + The module contains implementations of all key cache interface functions + employed by partitioned key caches. + + A partitioned key cache is a collection of structures for simple key caches + called key cache partitions. Any page from a file can be placed into a buffer + of only one partition. The number of the partition is calculated from + the file number and the position of the page in the file, and it's always the + same for the page. The function that maps pages into partitions takes care + of even distribution of pages among partitions. + + Partition key cache mitigate one of the major problem of simple key cache: + thread contention for key cache lock (mutex). Every call of a key cache + interface function must acquire this lock. So threads compete for this lock + even in the case when they have acquired shared locks for the file and + pages they want read from are in the key cache buffers. + When working with a partitioned key cache any key cache interface function + that needs only one page has to acquire the key cache lock only for the + partition the page is ascribed to. This makes the chances for threads not + compete for the same key cache lock better. Unfortunately if we use a + partitioned key cache with N partitions for B-tree indexes we can't say + that the chances becomes N times less. The fact is that any index lookup + operation requires reading from the root page that, for any index, is always + ascribed to the same partition. To resolve this problem we should have + employed more sophisticated mechanisms of working with root pages. + + Currently the number of partitions in a partitioned key cache is limited + by 64. We could increase this limit. Simultaneously we would have to increase + accordingly the size of the bitmap dirty_part_map from the MYISAM_SHARE + structure. + +******************************************************************************/ + +/* Control block for a partitioned key cache */ + +typedef struct st_partitioned_key_cache_cb +{ + my_bool key_cache_inited; /*<=> control block is allocated */ + SIMPLE_KEY_CACHE_CB **partition_array; /* the key cache partitions */ + size_t key_cache_mem_size; /* specified size of the cache memory */ + uint key_cache_block_size; /* size of the page buffer of a cache block */ + uint partitions; /* number of partitions in the key cache */ +} PARTITIONED_KEY_CACHE_CB; + +static +void end_partitioned_key_cache(PARTITIONED_KEY_CACHE_CB *keycache, + my_bool cleanup); + +static int +reset_partitioned_key_cache_counters(const char *name, + PARTITIONED_KEY_CACHE_CB *keycache); + +/* + Determine the partition to which the index block to read is ascribed + + SYNOPSIS + get_key_cache_partition() + keycache pointer to the control block of a partitioned key cache + file handler for the file for the block of data to be read + filepos position of the block of data in the file + + DESCRIPTION + The function determines the number of the partition in whose buffer the + block from 'file' at the position filepos has to be placed for reading. + The function returns the control block of the simple key cache for this + partition to the caller. + + RETURN VALUE + The pointer to the control block of the partition to which the specified + file block is ascribed. +*/ + +static +SIMPLE_KEY_CACHE_CB * +get_key_cache_partition(PARTITIONED_KEY_CACHE_CB *keycache, + File file, my_off_t filepos) +{ + uint i= KEYCACHE_BASE_EXPR(file, filepos) % keycache->partitions; + return keycache->partition_array[i]; +} + + +/* + Determine the partition to which the index block to write is ascribed + + SYNOPSIS + get_key_cache_partition() + keycache pointer to the control block of a partitioned key cache + file handler for the file for the block of data to be read + filepos position of the block of data in the file + dirty_part_map pointer to the bitmap of dirty partitions for the file + + DESCRIPTION + The function determines the number of the partition in whose buffer the + block from 'file' at the position filepos has to be placed for writing and + marks the partition as dirty in the dirty_part_map bitmap. + The function returns the control block of the simple key cache for this + partition to the caller. + + RETURN VALUE + The pointer to the control block of the partition to which the specified + file block is ascribed. +*/ + +static SIMPLE_KEY_CACHE_CB +*get_key_cache_partition_for_write(PARTITIONED_KEY_CACHE_CB *keycache, + File file, my_off_t filepos, + ulonglong* dirty_part_map) +{ + uint i= KEYCACHE_BASE_EXPR( file, filepos) % keycache->partitions; + *dirty_part_map|= 1ULL << i; + return keycache->partition_array[i]; +} + + +/* + Initialize a partitioned key cache + + SYNOPSIS + init_partitioned_key_cache() + keycache pointer to the control block of a partitioned key cache + key_cache_block_size size of blocks to keep cached data + use_mem total memory to use for all key cache partitions + division_limit division limit (may be zero) + age_threshold age threshold (may be zero) + + DESCRIPTION + This function is the implementation of the init_key_cache + interface function that is employed by partitioned key caches. + + The function builds and initializes an array of simple key caches, + and then initializes the control block structure of the type + PARTITIONED_KEY_CACHE_CB that is used for a partitioned key + cache. The parameter keycache is supposed to point to this + structure. The number of partitions in the partitioned key cache + to be built must be passed through the field 'partitions' of this + structure. + The parameter key_cache_block_size specifies the size of the + blocks in the the simple key caches to be built. + The parameters division_limit and age_threshold determine the initial + values of those characteristics of the simple key caches that are used for + midpoint insertion strategy. The parameter use_mem specifies the total + amount of memory to be allocated for the key cache blocks in all simple key + caches and for all auxiliary structures. + + RETURN VALUE + total number of blocks in key cache partitions, if successful, + <= 0 - otherwise. + + NOTES + If keycache->key_cache_inited != 0 then we assume that the memory for + the array of partitions has been already allocated. + + It's assumed that no two threads call this function simultaneously + referring to the same key cache handle. +*/ + +static +int init_partitioned_key_cache(PARTITIONED_KEY_CACHE_CB *keycache, + uint key_cache_block_size, + size_t use_mem, uint division_limit, + uint age_threshold, uint changed_blocks_hash_size) +{ + int i; + size_t mem_per_cache; + size_t mem_decr; + int cnt; + SIMPLE_KEY_CACHE_CB *partition; + SIMPLE_KEY_CACHE_CB **partition_ptr; + uint partitions= keycache->partitions; + int blocks= 0; + DBUG_ENTER("partitioned_init_key_cache"); + + keycache->key_cache_block_size = key_cache_block_size; + + if (keycache->key_cache_inited) + partition_ptr= keycache->partition_array; + else + { + if(!(partition_ptr= + (SIMPLE_KEY_CACHE_CB **) my_malloc(key_memory_KEY_CACHE, + sizeof(SIMPLE_KEY_CACHE_CB *) * + partitions, MYF(MY_WME)))) + DBUG_RETURN(-1); + bzero(partition_ptr, sizeof(SIMPLE_KEY_CACHE_CB *) * partitions); + keycache->partition_array= partition_ptr; + } + + mem_per_cache = use_mem / partitions; + mem_decr= mem_per_cache / 5; + + for (i= 0; i < (int) partitions; i++) + { + my_bool key_cache_inited= keycache->key_cache_inited; + if (key_cache_inited) + partition= *partition_ptr; + else + { + if (!(partition= + (SIMPLE_KEY_CACHE_CB *) my_malloc(key_memory_KEY_CACHE, + sizeof(SIMPLE_KEY_CACHE_CB), + MYF(MY_WME)))) + continue; + partition->key_cache_inited= 0; + } + + cnt= init_simple_key_cache(partition, key_cache_block_size, mem_per_cache, + division_limit, age_threshold, + changed_blocks_hash_size); + if (cnt <= 0) + { + end_simple_key_cache(partition, 1); + if (!key_cache_inited) + { + my_free(partition); + partition= 0; + } + if ((i == 0 && cnt < 0) || i > 0) + { + /* + Here we have two cases: + 1. i == 0 and cnt < 0 + cnt < 0 => mem_per_cache is not big enough to allocate minimal + number of key blocks in the key cache of the partition. + Decrease the the number of the partitions by 1 and start again. + 2. i > 0 + There is not enough memory for one of the succeeding partitions. + Just skip this partition decreasing the number of partitions in + the key cache by one. + Do not change the value of mem_per_cache in both cases. + */ + if (key_cache_inited) + { + my_free(partition); + partition= 0; + if(key_cache_inited) + memmove(partition_ptr, partition_ptr+1, + sizeof(partition_ptr)*(partitions-i-1)); + } + if (!--partitions) + break; + } + else + { + /* + We come here when i == 0 && cnt == 0. + cnt == 0 => the memory allocator fails to allocate a block of + memory of the size mem_per_cache. Decrease the value of + mem_per_cache without changing the current number of partitions + and start again. Make sure that such a decrease may happen not + more than 5 times in total. + */ + if (use_mem <= mem_decr) + break; + use_mem-= mem_decr; + } + i--; + mem_per_cache= use_mem/partitions; + continue; + } + else + { + blocks+= cnt; + *partition_ptr++= partition; + } + } + + keycache->partitions= partitions= (uint) (partition_ptr-keycache->partition_array); + keycache->key_cache_mem_size= mem_per_cache * partitions; + for (i= 0; i < (int) partitions; i++) + keycache->partition_array[i]->hash_factor= partitions; + + keycache->key_cache_inited= 1; + + if (!partitions) + blocks= -1; + + DBUG_RETURN(blocks); +} + + +/* + Resize a partitioned key cache + + SYNOPSIS + resize_partitioned_key_cache() + keycache pointer to the control block of a partitioned key cache + key_cache_block_size size of blocks to keep cached data + use_mem total memory to use for the new key cache + division_limit new division limit (if not zero) + age_threshold new age threshold (if not zero) + + DESCRIPTION + This function is the implementation of the resize_key_cache interface + function that is employed by partitioned key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type PARTITIONED_KEY_CACHE_CB for the + partitioned key cache to be resized. + The parameter key_cache_block_size specifies the new size of the blocks in + the simple key caches that comprise the partitioned key cache. + The parameters division_limit and age_threshold determine the new initial + values of those characteristics of the simple key cache that are used for + midpoint insertion strategy. The parameter use-mem specifies the total + amount of memory to be allocated for the key cache blocks in all new + simple key caches and for all auxiliary structures. + + RETURN VALUE + number of blocks in the key cache, if successful, + 0 - otherwise. + + NOTES. + The function first calls prepare_resize_simple_key_cache for each simple + key cache effectively flushing all dirty pages from it and destroying + the key cache. Then init_partitioned_key_cache is called. This call builds + a new array of simple key caches containing the same number of elements + as the old one. After this the function calls the function + finish_resize_simple_key_cache for each simple key cache from this array. + + This implementation doesn't block the calls and executions of other + functions from the key cache interface. However it assumes that the + calls of resize_partitioned_key_cache itself are serialized. +*/ + +static +int resize_partitioned_key_cache(PARTITIONED_KEY_CACHE_CB *keycache, + uint key_cache_block_size, + size_t use_mem, uint division_limit, + uint age_threshold, + uint changed_blocks_hash_size) +{ + uint i; + uint partitions= keycache->partitions; + my_bool cleanup= use_mem == 0; + int blocks= -1; + int err= 0; + DBUG_ENTER("partitioned_resize_key_cache"); + if (cleanup) + { + end_partitioned_key_cache(keycache, 0); + DBUG_RETURN(-1); + } + for (i= 0; i < partitions; i++) + { + err|= prepare_resize_simple_key_cache(keycache->partition_array[i], 1); + } + if (!err) + blocks= init_partitioned_key_cache(keycache, key_cache_block_size, + use_mem, division_limit, age_threshold, + changed_blocks_hash_size); + if (blocks > 0) + { + for (i= 0; i < partitions; i++) + { + keycache_pthread_mutex_lock(&keycache->partition_array[i]->cache_lock); + finish_resize_simple_key_cache(keycache->partition_array[i]); + } + } + DBUG_RETURN(blocks); +} + + +/* + Change key cache parameters of a partitioned key cache + + SYNOPSIS + partitioned_change_key_cache_param() + keycache pointer to the control block of a partitioned key cache + division_limit new division limit (if not zero) + age_threshold new age threshold (if not zero) + + DESCRIPTION + This function is the implementation of the change_key_cache_param interface + function that is employed by partitioned key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type PARTITIONED_KEY_CACHE_CB for the simple + key cache where new values of the division limit and the age threshold used + for midpoint insertion strategy are to be set. The parameters + division_limit and age_threshold provide these new values. + + RETURN VALUE + none + + NOTES + The function just calls change_simple_key_cache_param for each element from + the array of simple caches that comprise the partitioned key cache. +*/ + +static +void change_partitioned_key_cache_param(PARTITIONED_KEY_CACHE_CB *keycache, + uint division_limit, + uint age_threshold) +{ + uint i; + uint partitions= keycache->partitions; + DBUG_ENTER("partitioned_change_key_cache_param"); + for (i= 0; i < partitions; i++) + { + change_simple_key_cache_param(keycache->partition_array[i], division_limit, + age_threshold); + } + DBUG_VOID_RETURN; +} + + +/* + Destroy a partitioned key cache + + SYNOPSIS + end_partitioned_key_cache() + keycache pointer to the control block of a partitioned key cache + cleanup <=> complete free (free also control block structures + for all simple key caches) + + DESCRIPTION + This function is the implementation of the end_key_cache interface + function that is employed by partitioned key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type PARTITIONED_KEY_CACHE_CB for the + partitioned key cache to be destroyed. + The function frees the memory allocated for the cache blocks and + auxiliary structures used by simple key caches that comprise the + partitioned key cache. If the value of the parameter cleanup is TRUE + then even the memory used for control blocks of the simple key caches + and the array of pointers to them are freed. + + RETURN VALUE + none +*/ + +static +void end_partitioned_key_cache(PARTITIONED_KEY_CACHE_CB *keycache, + my_bool cleanup) +{ + uint i; + uint partitions= keycache->partitions; + DBUG_ENTER("partitioned_end_key_cache"); + DBUG_PRINT("enter", ("key_cache: %p", keycache)); + + for (i= 0; i < partitions; i++) + { + end_simple_key_cache(keycache->partition_array[i], cleanup); + } + if (cleanup) + { + for (i= 0; i < partitions; i++) + my_free(keycache->partition_array[i]); + my_free(keycache->partition_array); + keycache->key_cache_inited= 0; + } + DBUG_VOID_RETURN; +} + + +/* + Read a block of data from a partitioned key cache into a buffer + + SYNOPSIS + + partitioned_key_cache_read() + keycache pointer to the control block of a partitioned key cache + file handler for the file for the block of data to be read + filepos position of the block of data in the file + level determines the weight of the data + buff buffer to where the data must be placed + length length of the buffer + block_length length of the read data from a key cache block + return_buffer return pointer to the key cache buffer with the data + + DESCRIPTION + This function is the implementation of the key_cache_read interface + function that is employed by partitioned key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type PARTITIONED_KEY_CACHE_CB for a + partitioned key cache. + In a general case the function reads a block of data from the key cache + into the buffer buff of the size specified by the parameter length. The + beginning of the block of data to be read is specified by the parameters + file and filepos. The length of the read data is the same as the length + of the buffer. The data is read into the buffer in key_cache_block_size + increments. To read each portion the function first finds out in what + partition of the key cache this portion(page) is to be saved, and calls + simple_key_cache_read with the pointer to the corresponding simple key as + its first parameter. + If the parameter return_buffer is not ignored and its value is TRUE, and + the data to be read of the specified size block_length can be read from one + key cache buffer, then the function returns a pointer to the data in the + key cache buffer. + The function takes into account parameters block_length and return buffer + only in a single-threaded environment. + The parameter 'level' is used only by the midpoint insertion strategy + when the data or its portion cannot be found in the key cache. + + RETURN VALUE + Returns address from where the data is placed if successful, 0 - otherwise. +*/ + +static +uchar *partitioned_key_cache_read(PARTITIONED_KEY_CACHE_CB *keycache, + File file, my_off_t filepos, int level, + uchar *buff, uint length, + uint block_length __attribute__((unused)), + int return_buffer __attribute__((unused))) +{ + uint r_length; + uint offset= (uint) (filepos % keycache->key_cache_block_size); + uchar *start= buff; + DBUG_ENTER("partitioned_key_cache_read"); + DBUG_PRINT("enter", ("fd: %u pos: %lu length: %u", + (uint) file, (ulong) filepos, length)); + + + /* Read data in key_cache_block_size increments */ + do + { + SIMPLE_KEY_CACHE_CB *partition= get_key_cache_partition(keycache, + file, filepos); + uchar *ret_buff= 0; + r_length= length; + set_if_smaller(r_length, keycache->key_cache_block_size - offset); + ret_buff= simple_key_cache_read((void *) partition, + file, filepos, level, + buff, r_length, + block_length, return_buffer); + if (ret_buff == 0) + DBUG_RETURN(0); + filepos+= r_length; + buff+= r_length; + offset= 0; + } while ((length-= r_length)); + + DBUG_RETURN(start); +} + + +/* + Insert a block of file data from a buffer into a partitioned key cache + + SYNOPSIS + partitioned_key_cache_insert() + keycache pointer to the control block of a partitioned key cache + file handler for the file to insert data from + filepos position of the block of data in the file to insert + level determines the weight of the data + buff buffer to read data from + length length of the data in the buffer + + DESCRIPTION + This function is the implementation of the key_cache_insert interface + function that is employed by partitioned key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type PARTITIONED_KEY_CACHE_CB for a + partitioned key cache. + The function writes a block of file data from a buffer into the key cache. + The buffer is specified with the parameters buff and length - the pointer + to the beginning of the buffer and its size respectively. It's assumed + that the buffer contains the data from 'file' allocated from the position + filepos. The data is copied from the buffer in key_cache_block_size + increments. For every portion of data the function finds out in what simple + key cache from the array of partitions the data must be stored, and after + this calls simple_key_cache_insert to copy the data into a key buffer of + this simple key cache. + The parameter level is used to set one characteristic for the key buffers + loaded with the data from buff. The characteristic is used only by the + midpoint insertion strategy. + + RETURN VALUE + 0 if a success, 1 - otherwise. + + NOTES + The function is used by MyISAM to move all blocks from a index file to + the key cache. It can be performed in parallel with reading the file data + from the key buffers by other threads. +*/ + +static +int partitioned_key_cache_insert(PARTITIONED_KEY_CACHE_CB *keycache, + File file, my_off_t filepos, int level, + uchar *buff, uint length) +{ + uint w_length; + uint offset= (uint) (filepos % keycache->key_cache_block_size); + DBUG_ENTER("partitioned_key_cache_insert"); + DBUG_PRINT("enter", ("fd: %u pos: %lu length: %u", + (uint) file,(ulong) filepos, length)); + + + /* Write data in key_cache_block_size increments */ + do + { + SIMPLE_KEY_CACHE_CB *partition= get_key_cache_partition(keycache, + file, filepos); + w_length= length; + set_if_smaller(w_length, keycache->key_cache_block_size - offset); + if (simple_key_cache_insert((void *) partition, + file, filepos, level, + buff, w_length)) + DBUG_RETURN(1); + + filepos+= w_length; + buff+= w_length; + offset = 0; + } while ((length-= w_length)); + + DBUG_RETURN(0); +} + + +/* + Write data from a buffer into a partitioned key cache + + SYNOPSIS + + partitioned_key_cache_write() + keycache pointer to the control block of a partitioned key cache + file handler for the file to write data to + filepos position in the file to write data to + level determines the weight of the data + buff buffer with the data + length length of the buffer + dont_write if is 0 then all dirty pages involved in writing + should have been flushed from key cache + file_extra maps of key cache partitions containing + dirty pages from file + + DESCRIPTION + This function is the implementation of the key_cache_write interface + function that is employed by partitioned key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type PARTITIONED_KEY_CACHE_CB for a + partitioned key cache. + In a general case the function copies data from a buffer into the key + cache. The buffer is specified with the parameters buff and length - + the pointer to the beginning of the buffer and its size respectively. + It's assumed the buffer contains the data to be written into 'file' + starting from the position filepos. The data is copied from the buffer + in key_cache_block_size increments. For every portion of data the + function finds out in what simple key cache from the array of partitions + the data must be stored, and after this calls simple_key_cache_write to + copy the data into a key buffer of this simple key cache. + If the value of the parameter dont_write is FALSE then the function + also writes the data into file. + The parameter level is used to set one characteristic for the key buffers + filled with the data from buff. The characteristic is employed only by + the midpoint insertion strategy. + The parameter file_expra provides a pointer to the shared bitmap of + the partitions that may contains dirty pages for the file. This bitmap + is used to optimize the function flush_partitioned_key_cache_blocks. + + RETURN VALUE + 0 if a success, 1 - otherwise. + + NOTES + This implementation exploits the fact that the function is called only + when a thread has got an exclusive lock for the key file. +*/ + +static +int partitioned_key_cache_write(PARTITIONED_KEY_CACHE_CB *keycache, + File file, void *file_extra, + my_off_t filepos, int level, + uchar *buff, uint length, + uint block_length __attribute__((unused)), + int dont_write) +{ + uint w_length; + ulonglong *part_map= (ulonglong *) file_extra; + uint offset= (uint) (filepos % keycache->key_cache_block_size); + DBUG_ENTER("partitioned_key_cache_write"); + DBUG_PRINT("enter", + ("fd: %u pos: %lu length: %u block_length: %u" + " key_block_length: %u", + (uint) file, (ulong) filepos, length, block_length, + keycache ? keycache->key_cache_block_size : 0)); + + + /* Write data in key_cache_block_size increments */ + do + { + SIMPLE_KEY_CACHE_CB *partition= get_key_cache_partition_for_write(keycache, + file, + filepos, + part_map); + w_length = length; + set_if_smaller(w_length, keycache->key_cache_block_size - offset ); + if (simple_key_cache_write(partition, + file, 0, filepos, level, + buff, w_length, block_length, + dont_write)) + DBUG_RETURN(1); + + filepos+= w_length; + buff+= w_length; + offset= 0; + } while ((length-= w_length)); + + DBUG_RETURN(0); +} + + +/* + Flush all blocks for a file from key buffers of a partitioned key cache + + SYNOPSIS + + flush_partitioned_key_cache_blocks() + keycache pointer to the control block of a partitioned key cache + file handler for the file to flush to + file_extra maps of key cache partitions containing + dirty pages from file (not used) + flush_type type of the flush operation + + DESCRIPTION + This function is the implementation of the flush_key_blocks interface + function that is employed by partitioned key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type PARTITIONED_KEY_CACHE_CB for a + partitioned key cache. + In a general case the function flushes the data from all dirty key + buffers related to the file 'file' into this file. The function does + exactly this if the value of the parameter type is FLUSH_KEEP. If the + value of this parameter is FLUSH_RELEASE, the function additionally + releases the key buffers containing data from 'file' for new usage. + If the value of the parameter type is FLUSH_IGNORE_CHANGED the function + just releases the key buffers containing data from 'file'. + The function performs the operation by calling the function + flush_simple_key_cache_blocks for the elements of the array of the + simple key caches that comprise the partitioned key_cache. If the value + of the parameter type is FLUSH_KEEP s_flush_key_blocks is called only + for the partitions with possibly dirty pages marked in the bitmap + pointed to by the parameter file_extra. + + RETURN + 0 ok + 1 error + + NOTES + This implementation exploits the fact that the function is called only + when a thread has got an exclusive lock for the key file. +*/ + +static +int flush_partitioned_key_cache_blocks(PARTITIONED_KEY_CACHE_CB *keycache, + File file, void *file_extra, + enum flush_type type) +{ + uint i; + uint partitions= keycache->partitions; + int err= 0; + ulonglong *dirty_part_map= (ulonglong *) file_extra; + DBUG_ENTER("partitioned_flush_key_blocks"); + DBUG_PRINT("enter", ("keycache: %p", keycache)); + + for (i= 0; i < partitions; i++) + { + SIMPLE_KEY_CACHE_CB *partition= keycache->partition_array[i]; + if ((type == FLUSH_KEEP || type == FLUSH_FORCE_WRITE) && + !((*dirty_part_map) & ((ulonglong) 1 << i))) + continue; + err|= MY_TEST(flush_simple_key_cache_blocks(partition, file, 0, type)); + } + *dirty_part_map= 0; + + DBUG_RETURN(err); +} + + +/* + Reset the counters of a partitioned key cache + + SYNOPSIS + reset_partitioned_key_cache_counters() + name the name of a key cache + keycache pointer to the control block of a partitioned key cache + + DESCRIPTION + This function is the implementation of the reset_key_cache_counters + interface function that is employed by partitioned key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type PARTITIONED_KEY_CACHE_CB for a partitioned + key cache. + This function resets the values of the statistical counters of the simple + key caches comprising partitioned key cache to 0. It does it by calling + reset_simple_key_cache_counters for each key cache partition. + The parameter name is currently not used. + + RETURN + 0 on success (always because it can't fail) +*/ + +static int +reset_partitioned_key_cache_counters(const char *name __attribute__((unused)), + PARTITIONED_KEY_CACHE_CB *keycache) +{ + uint i; + uint partitions= keycache->partitions; + DBUG_ENTER("partitioned_reset_key_cache_counters"); + + for (i = 0; i < partitions; i++) + { + reset_simple_key_cache_counters(name, keycache->partition_array[i]); + } + DBUG_RETURN(0); +} + + +/* + Get statistics for a partition key cache + + SYNOPSIS + get_partitioned_key_cache_statistics() + keycache pointer to the control block of a partitioned key cache + partition_no partition number to get statistics for + key_cache_stats OUT pointer to the structure for the returned statistics + + DESCRIPTION + This function is the implementation of the get_key_cache_statistics + interface function that is employed by partitioned key caches. + The function takes the parameter keycache as a pointer to the + control block structure of the type PARTITIONED_KEY_CACHE_CB for + a partitioned key cache. + If the value of the parameter partition_no is equal to 0 then aggregated + statistics for all partitions is returned in the fields of the + structure key_cache_stat of the type KEY_CACHE_STATISTICS . Otherwise + the function returns data for the partition number partition_no of the + key cache in the structure key_cache_stat. (Here partitions are numbered + starting from 1.) + + RETURN + none +*/ + +static +void +get_partitioned_key_cache_statistics(PARTITIONED_KEY_CACHE_CB *keycache, + uint partition_no, + KEY_CACHE_STATISTICS *keycache_stats) +{ + uint i; + SIMPLE_KEY_CACHE_CB *partition; + uint partitions= keycache->partitions; + DBUG_ENTER("get_partitioned_key_cache_statistics"); + + if (partition_no != 0) + { + partition= keycache->partition_array[partition_no-1]; + get_simple_key_cache_statistics((void *) partition, 0, keycache_stats); + DBUG_VOID_RETURN; + } + bzero(keycache_stats, sizeof(KEY_CACHE_STATISTICS)); + keycache_stats->mem_size= (longlong) keycache->key_cache_mem_size; + keycache_stats->block_size= (longlong) keycache->key_cache_block_size; + for (i = 0; i < partitions; i++) + { + partition= keycache->partition_array[i]; + keycache_stats->blocks_used+= partition->blocks_used; + keycache_stats->blocks_unused+= partition->blocks_unused; + keycache_stats->blocks_changed+= partition->global_blocks_changed; + keycache_stats->blocks_warm+= partition->warm_blocks; + keycache_stats->read_requests+= partition->global_cache_r_requests; + keycache_stats->reads+= partition->global_cache_read; + keycache_stats->write_requests+= partition->global_cache_w_requests; + keycache_stats->writes+= partition->global_cache_write; + } + DBUG_VOID_RETURN; +} + +/* + The array of pointers to the key cache interface functions used by + partitioned key caches. Any partitioned key cache object caches exploits + this array. + + The current implementation of these functions does not allow to call + them from the MySQL server code directly. The key cache interface + wrappers must be used for this purpose. +*/ + +static KEY_CACHE_FUNCS partitioned_key_cache_funcs = +{ + (INIT_KEY_CACHE) init_partitioned_key_cache, + (RESIZE_KEY_CACHE) resize_partitioned_key_cache, + (CHANGE_KEY_CACHE_PARAM) change_partitioned_key_cache_param, + (KEY_CACHE_READ) partitioned_key_cache_read, + (KEY_CACHE_INSERT) partitioned_key_cache_insert, + (KEY_CACHE_WRITE) partitioned_key_cache_write, + (FLUSH_KEY_BLOCKS) flush_partitioned_key_cache_blocks, + (RESET_KEY_CACHE_COUNTERS) reset_partitioned_key_cache_counters, + (END_KEY_CACHE) end_partitioned_key_cache, + (GET_KEY_CACHE_STATISTICS) get_partitioned_key_cache_statistics, +}; + + +/****************************************************************************** + Key Cache Interface Module + + The module contains wrappers for all key cache interface functions. + + Currently there are key caches of two types: simple key caches and + partitioned key caches. Each type (class) has its own implementation of the + basic key cache operations used the MyISAM storage engine. The pointers + to the implementation functions are stored in two static structures of the + type KEY_CACHE_FUNC: simple_key_cache_funcs - for simple key caches, and + partitioned_key_cache_funcs - for partitioned key caches. When a key cache + object is created the constructor procedure init_key_cache places a pointer + to the corresponding table into one of its fields. The procedure also + initializes a control block for the key cache oject and saves the pointer + to this block in another field of the key cache object. + When a key cache wrapper function is invoked for a key cache object to + perform a basic key cache operation it looks into the interface table + associated with the key cache oject and calls the corresponding + implementation of the operation. It passes the saved key cache control + block to this implementation. If, for some reasons, the control block + has not been fully initialized yet, the wrapper function either does not + do anything or, in the case when it perform a read/write operation, the + function do it directly through the system i/o functions. + + As we can see the model with which the key cache interface is supported + as quite conventional for interfaces in general. + +******************************************************************************/ + +static +int repartition_key_cache_internal(KEY_CACHE *keycache, + uint key_cache_block_size, size_t use_mem, + uint division_limit, uint age_threshold, + uint changed_blocks_hash_size, + uint partitions, my_bool use_op_lock); + +/* + Initialize a key cache : internal + + SYNOPSIS + init_key_cache_internal() + keycache pointer to the key cache to be initialized + key_cache_block_size size of blocks to keep cached data + use_mem total memory to use for cache buffers/structures + division_limit division limit (may be zero) + age_threshold age threshold (may be zero) + changed_blocks_hash_size Number of hash buckets to hold a link of different + files. Should be proportional to number of different + files sused. + partitions Number of partitions in the key cache + use_op_lock if TRUE use keycache->op_lock, otherwise - ignore it + + DESCRIPTION + The function performs the actions required from init_key_cache(). + It has an additional parameter: use_op_lock. When the parameter + is TRUE than the function initializes keycache->op_lock if needed, + then locks it, and unlocks it before the return. Otherwise the actions + with the lock are omitted. + + RETURN VALUE + total number of blocks in key cache partitions, if successful, + <= 0 - otherwise. + + NOTES + if keycache->key_cache_inited != 0 we assume that the memory + for the control block of the key cache has been already allocated. +*/ + +static +int init_key_cache_internal(KEY_CACHE *keycache, uint key_cache_block_size, + size_t use_mem, uint division_limit, + uint age_threshold, uint changed_blocks_hash_size, + uint partitions, + my_bool use_op_lock) +{ + void *keycache_cb; + int blocks; + if (keycache->key_cache_inited) + { + if (use_op_lock) + pthread_mutex_lock(&keycache->op_lock); + keycache_cb= keycache->keycache_cb; + } + else + { + if (partitions == 0) + { + if (!(keycache_cb= (void *) my_malloc(key_memory_KEY_CACHE, + sizeof(SIMPLE_KEY_CACHE_CB), + MYF(0)))) + return 0; + ((SIMPLE_KEY_CACHE_CB *) keycache_cb)->key_cache_inited= 0; + keycache->key_cache_type= SIMPLE_KEY_CACHE; + keycache->interface_funcs= &simple_key_cache_funcs; + } + else + { + if (!(keycache_cb= (void *) my_malloc(key_memory_KEY_CACHE, + sizeof(PARTITIONED_KEY_CACHE_CB), + MYF(0)))) + return 0; + ((PARTITIONED_KEY_CACHE_CB *) keycache_cb)->key_cache_inited= 0; + keycache->key_cache_type= PARTITIONED_KEY_CACHE; + keycache->interface_funcs= &partitioned_key_cache_funcs; + } + /* + Initialize op_lock if it's not initialized before. + The mutex may have been initialized before if we are being called + from repartition_key_cache_internal(). + */ + if (use_op_lock) + pthread_mutex_init(&keycache->op_lock, MY_MUTEX_INIT_FAST); + keycache->keycache_cb= keycache_cb; + keycache->key_cache_inited= 1; + if (use_op_lock) + pthread_mutex_lock(&keycache->op_lock); + } + + if (partitions != 0) + { + ((PARTITIONED_KEY_CACHE_CB *) keycache_cb)->partitions= partitions; + } + keycache->can_be_used= 0; + blocks= keycache->interface_funcs->init(keycache_cb, key_cache_block_size, + use_mem, division_limit, + age_threshold, changed_blocks_hash_size); + keycache->partitions= partitions ? + ((PARTITIONED_KEY_CACHE_CB *) keycache_cb)->partitions : + 0; + DBUG_ASSERT(partitions <= MAX_KEY_CACHE_PARTITIONS); + keycache->key_cache_mem_size= + keycache->partitions ? + ((PARTITIONED_KEY_CACHE_CB *) keycache_cb)->key_cache_mem_size : + ((SIMPLE_KEY_CACHE_CB *) keycache_cb)->key_cache_mem_size; + if (blocks > 0) + keycache->can_be_used= 1; + if (use_op_lock) + pthread_mutex_unlock(&keycache->op_lock); + return blocks; +} + + +/* + Initialize a key cache + + SYNOPSIS + init_key_cache() + keycache pointer to the key cache to be initialized + key_cache_block_size size of blocks to keep cached data + use_mem total memory to use for cache buffers/structures + division_limit division limit (may be zero) + age_threshold age threshold (may be zero) + partitions number of partitions in the key cache + + DESCRIPTION + The function creates a control block structure for a key cache and + places the pointer to this block in the structure keycache. + If the value of the parameter 'partitions' is 0 then a simple key cache + is created. Otherwise a partitioned key cache with the specified number + of partitions is created. + The parameter key_cache_block_size specifies the size of the blocks in + the key cache to be created. The parameters division_limit and + age_threshold determine the initial values of those characteristics of + the key cache that are used for midpoint insertion strategy. The parameter + use_mem specifies the total amount of memory to be allocated for the + key cache buffers and for all auxiliary structures. + The function calls init_key_cache_internal() to perform all these actions + with the last parameter set to TRUE. + + RETURN VALUE + total number of blocks in key cache partitions, if successful, + <= 0 - otherwise. + + NOTES + It's assumed that no two threads call this function simultaneously + referring to the same key cache handle. +*/ + +int init_key_cache(KEY_CACHE *keycache, uint key_cache_block_size, + size_t use_mem, uint division_limit, + uint age_threshold, uint changed_blocks_hash_size, + uint partitions) +{ + return init_key_cache_internal(keycache, key_cache_block_size, use_mem, + division_limit, age_threshold, + changed_blocks_hash_size, partitions, 1); +} + + +/* + Resize a key cache + + SYNOPSIS + resize_key_cache() + keycache pointer to the key cache to be resized + key_cache_block_size size of blocks to keep cached data + use_mem total memory to use for the new key cache + division_limit new division limit (if not zero) + age_threshold new age threshold (if not zero) + + DESCRIPTION + The function operates over the key cache key cache. + The parameter key_cache_block_size specifies the new size of the block + buffers in the key cache. The parameters division_limit and age_threshold + determine the new initial values of those characteristics of the key cache + that are used for midpoint insertion strategy. The parameter use_mem + specifies the total amount of memory to be allocated for the key cache + buffers and for all auxiliary structures. + + RETURN VALUE + number of blocks in the key cache, if successful, + 0 - otherwise. + + NOTES + The function does not block the calls and executions of other functions + from the key cache interface. However it assumes that the calls of + resize_key_cache itself are serialized. + + Currently the function is called when the values of the variables + key_buffer_size and/or key_cache_block_size are being reset for + the key cache keycache. +*/ + +int resize_key_cache(KEY_CACHE *keycache, uint key_cache_block_size, + size_t use_mem, uint division_limit, uint age_threshold, + uint changed_blocks_hash_size) +{ + int blocks= -1; + if (keycache->key_cache_inited) + { + pthread_mutex_lock(&keycache->op_lock); + if ((uint) keycache->param_partitions != keycache->partitions && use_mem) + blocks= repartition_key_cache_internal(keycache, + key_cache_block_size, use_mem, + division_limit, age_threshold, + changed_blocks_hash_size, + (uint) keycache->param_partitions, + 0); + else + { + blocks= keycache->interface_funcs->resize(keycache->keycache_cb, + key_cache_block_size, + use_mem, division_limit, + age_threshold, + changed_blocks_hash_size); + + if (keycache->partitions) + keycache->partitions= + ((PARTITIONED_KEY_CACHE_CB *)(keycache->keycache_cb))->partitions; + } + + keycache->key_cache_mem_size= + keycache->partitions ? + ((PARTITIONED_KEY_CACHE_CB *)(keycache->keycache_cb))->key_cache_mem_size : + ((SIMPLE_KEY_CACHE_CB *)(keycache->keycache_cb))->key_cache_mem_size; + + keycache->can_be_used= (blocks >= 0); + pthread_mutex_unlock(&keycache->op_lock); + } + return blocks; +} + + +/* + Change key cache parameters of a key cache + + SYNOPSIS + change_key_cache_param() + keycache pointer to the key cache to change parameters for + division_limit new division limit (if not zero) + age_threshold new age threshold (if not zero) + + DESCRIPTION + The function sets new values of the division limit and the age threshold + used when the key cache keycach employs midpoint insertion strategy. + The parameters division_limit and age_threshold provide these new values. + + RETURN VALUE + none + + NOTES + Currently the function is called when the values of the variables + key_cache_division_limit and/or key_cache_age_threshold are being reset + for the key cache keycache. +*/ + +void change_key_cache_param(KEY_CACHE *keycache, uint division_limit, + uint age_threshold) +{ + if (keycache->key_cache_inited) + { + pthread_mutex_lock(&keycache->op_lock); + keycache->interface_funcs->change_param(keycache->keycache_cb, + division_limit, + age_threshold); + pthread_mutex_unlock(&keycache->op_lock); + } +} + + +/* + Destroy a key cache : internal + + SYNOPSIS + end_key_cache_internal() + keycache pointer to the key cache to be destroyed + cleanup <=> complete free + use_op_lock if TRUE use keycache->op_lock, otherwise - ignore it + + DESCRIPTION + The function performs the actions required from end_key_cache(). + It has an additional parameter: use_op_lock. When the parameter + is TRUE than the function destroys keycache->op_lock if cleanup is true. + Otherwise the action with the lock is omitted. + + RETURN VALUE + none +*/ + +static +void end_key_cache_internal(KEY_CACHE *keycache, my_bool cleanup, + my_bool use_op_lock) +{ + if (keycache->key_cache_inited) + { + keycache->interface_funcs->end(keycache->keycache_cb, cleanup); + if (cleanup) + { + if (keycache->keycache_cb) + { + my_free(keycache->keycache_cb); + keycache->keycache_cb= 0; + } + /* + We do not destroy op_lock if we are going to reuse the same key cache. + This happens if we are called from repartition_key_cache_internal(). + */ + if (use_op_lock) + pthread_mutex_destroy(&keycache->op_lock); + keycache->key_cache_inited= 0; + } + keycache->can_be_used= 0; + } +} + + +/* + Destroy a key cache + + SYNOPSIS + end_key_cache() + keycache pointer to the key cache to be destroyed + cleanup <=> complete free + + DESCRIPTION + The function frees the memory allocated for the cache blocks and + auxiliary structures used by the key cache keycache. If the value + of the parameter cleanup is TRUE then all resources used by the key + cache are to be freed. + The function calls end_key_cache_internal() to perform all these actions + with the last parameter set to TRUE. + + RETURN VALUE + none +*/ + +void end_key_cache(KEY_CACHE *keycache, my_bool cleanup) +{ + end_key_cache_internal(keycache, cleanup, 1); +} + + +/* + Read a block of data from a key cache into a buffer + + SYNOPSIS + + key_cache_read() + keycache pointer to the key cache to read data from + file handler for the file for the block of data to be read + filepos position of the block of data in the file + level determines the weight of the data + buff buffer to where the data must be placed + length length of the buffer + block_length length of the data read from a key cache block + return_buffer return pointer to the key cache buffer with the data + + DESCRIPTION + The function operates over buffers of the key cache keycache. + In a general case the function reads a block of data from the key cache + into the buffer buff of the size specified by the parameter length. The + beginning of the block of data to be read is specified by the parameters + file and filepos. The length of the read data is the same as the length + of the buffer. + If the parameter return_buffer is not ignored and its value is TRUE, and + the data to be read of the specified size block_length can be read from one + key cache buffer, then the function returns a pointer to the data in the + key cache buffer. + The parameter 'level' is used only by the midpoint insertion strategy + when the data or its portion cannot be found in the key cache. + The function reads data into the buffer directly from file if the control + block of the key cache has not been initialized yet. + + RETURN VALUE + Returns address from where the data is placed if successful, 0 - otherwise. + + NOTES. + Filepos must be a multiple of 'block_length', but it doesn't + have to be a multiple of key_cache_block_size; +*/ + +uchar *key_cache_read(KEY_CACHE *keycache, + File file, my_off_t filepos, int level, + uchar *buff, uint length, + uint block_length, int return_buffer) +{ + if (keycache->can_be_used) + return keycache->interface_funcs->read(keycache->keycache_cb, + file, filepos, level, + buff, length, + block_length, return_buffer); + + /* We can't use mutex here as the key cache may not be initialized */ + + if (my_pread(file, (uchar*) buff, length, filepos, MYF(MY_NABP))) + return (uchar *) 0; + + return buff; +} + + +/* + Insert a block of file data from a buffer into a key cache + + SYNOPSIS + key_cache_insert() + keycache pointer to the key cache to insert data into + file handler for the file to insert data from + filepos position of the block of data in the file to insert + level determines the weight of the data + buff buffer to read data from + length length of the data in the buffer + + DESCRIPTION + The function operates over buffers of the key cache keycache. + The function writes a block of file data from a buffer into the key cache. + The buffer is specified with the parameters buff and length - the pointer + to the beginning of the buffer and its size respectively. It's assumed + that the buffer contains the data from 'file' allocated from the position + filepos. + The parameter level is used to set one characteristic for the key buffers + loaded with the data from buff. The characteristic is used only by the + midpoint insertion strategy. + + RETURN VALUE + 0 if a success, 1 - otherwise. + + NOTES + The function is used by MyISAM to move all blocks from a index file to + the key cache. + It is assumed that it may be performed in parallel with reading the file + data from the key buffers by other threads. +*/ + +int key_cache_insert(KEY_CACHE *keycache, + File file, my_off_t filepos, int level, + uchar *buff, uint length) +{ + if (keycache->can_be_used) + return keycache->interface_funcs->insert(keycache->keycache_cb, + file, filepos, level, + buff, length); + return 0; +} + + +/* + Write data from a buffer into a key cache + + SYNOPSIS + + key_cache_write() + keycache pointer to the key cache to write data to + file handler for the file to write data to + filepos position in the file to write data to + level determines the weight of the data + buff buffer with the data + length length of the buffer + dont_write if is 0 then all dirty pages involved in writing + should have been flushed from key cache + file_extra pointer to optional file attributes + + DESCRIPTION + The function operates over buffers of the key cache keycache. + In a general case the function writes data from a buffer into the key + cache. The buffer is specified with the parameters buff and length - + the pointer to the beginning of the buffer and its size respectively. + It's assumed the buffer contains the data to be written into 'file' + starting from the position filepos. + If the value of the parameter dont_write is FALSE then the function + also writes the data into file. + The parameter level is used to set one characteristic for the key buffers + filled with the data from buff. The characteristic is employed only by + the midpoint insertion strategy. + The parameter file_expra may point to additional file attributes used + for optimization or other purposes. + The function writes data from the buffer directly into file if the control + block of the key cache has not been initialized yet. + + RETURN VALUE + 0 if a success, 1 - otherwise. + + NOTES + This implementation may exploit the fact that the function is called only + when a thread has got an exclusive lock for the key file. +*/ + +int key_cache_write(KEY_CACHE *keycache, + File file, void *file_extra, + my_off_t filepos, int level, + uchar *buff, uint length, + uint block_length, int force_write) +{ + if (keycache->can_be_used) + return keycache->interface_funcs->write(keycache->keycache_cb, + file, file_extra, + filepos, level, + buff, length, + block_length, force_write); + + /* We can't use mutex here as the key cache may not be initialized */ + if (my_pwrite(file, buff, length, filepos, MYF(MY_NABP | MY_WAIT_IF_FULL))) + return 1; + + return 0; +} + + +/* + Flush all blocks for a file from key buffers of a key cache + + SYNOPSIS + + flush_key_blocks() + keycache pointer to the key cache whose blocks are to be flushed + file handler for the file to flush to + file_extra maps of key cache (used for partitioned key caches) + flush_type type of the flush operation + + DESCRIPTION + The function operates over buffers of the key cache keycache. + In a general case the function flushes the data from all dirty key + buffers related to the file 'file' into this file. The function does + exactly this if the value of the parameter type is FLUSH_KEEP. If the + value of this parameter is FLUSH_RELEASE, the function additionally + releases the key buffers containing data from 'file' for new usage. + If the value of the parameter type is FLUSH_IGNORE_CHANGED the function + just releases the key buffers containing data from 'file'. + If the value of the parameter type is FLUSH_KEEP the function may use + the value of the parameter file_extra pointing to possibly dirty + partitions to optimize the operation for partitioned key caches. + + RETURN + 0 ok + 1 error + + NOTES + Any implementation of the function may exploit the fact that the function + is called only when a thread has got an exclusive lock for the key file. +*/ + +int flush_key_blocks(KEY_CACHE *keycache, + int file, void *file_extra, + enum flush_type type) +{ + if (keycache->can_be_used) + return keycache->interface_funcs->flush(keycache->keycache_cb, + file, file_extra, type); + return 0; +} + + +/* + Reset the counters of a key cache + + SYNOPSIS + reset_key_cache_counters() + name the name of a key cache (unused) + keycache pointer to the key cache for which to reset counters + + DESCRIPTION + This function resets the values of the statistical counters for the key + cache keycache. + The parameter name is currently not used. + + RETURN + 0 on success (always because it can't fail) + + NOTES + This procedure is used by process_key_caches() to reset the counters of all + currently used key caches, both the default one and the named ones. +*/ + +int reset_key_cache_counters(const char *name __attribute__((unused)), + KEY_CACHE *keycache, + void *unused __attribute__((unused))) +{ + int rc= 0; + if (keycache->key_cache_inited) + { + pthread_mutex_lock(&keycache->op_lock); + rc= keycache->interface_funcs->reset_counters(name, + keycache->keycache_cb); + pthread_mutex_unlock(&keycache->op_lock); + } + return rc; +} + + +/* + Get statistics for a key cache + + SYNOPSIS + get_key_cache_statistics() + keycache pointer to the key cache to get statistics for + partition_no partition number to get statistics for + key_cache_stats OUT pointer to the structure for the returned statistics + + DESCRIPTION + If the value of the parameter partition_no is equal to 0 then statistics + for the whole key cache keycache (aggregated statistics) is returned in the + fields of the structure key_cache_stat of the type KEY_CACHE_STATISTICS. + Otherwise the value of the parameter partition_no makes sense only for + a partitioned key cache. In this case the function returns statistics + for the partition with the specified number partition_no. + + RETURN + none +*/ + +void get_key_cache_statistics(KEY_CACHE *keycache, uint partition_no, + KEY_CACHE_STATISTICS *key_cache_stats) +{ + if (keycache->key_cache_inited) + { + pthread_mutex_lock(&keycache->op_lock); + keycache->interface_funcs->get_stats(keycache->keycache_cb, + partition_no, key_cache_stats); + pthread_mutex_unlock(&keycache->op_lock); + } +} + + +/* + Repartition a key cache : internal + + SYNOPSIS + repartition_key_cache_internal() + keycache pointer to the key cache to be repartitioned + key_cache_block_size size of blocks to keep cached data + use_mem total memory to use for the new key cache + division_limit new division limit (if not zero) + age_threshold new age threshold (if not zero) + partitions new number of partitions in the key cache + use_op_lock if TRUE use keycache->op_lock, otherwise - ignore it + + DESCRIPTION + The function performs the actions required from repartition_key_cache(). + It has an additional parameter: use_op_lock. When the parameter + is TRUE then the function locks keycache->op_lock at start and + unlocks it before the return. Otherwise the actions with the lock + are omitted. + + RETURN VALUE + number of blocks in the key cache, if successful, + 0 - otherwise. +*/ + +static +int repartition_key_cache_internal(KEY_CACHE *keycache, + uint key_cache_block_size, size_t use_mem, + uint division_limit, uint age_threshold, + uint changed_blocks_hash_size, + uint partitions, my_bool use_op_lock) +{ + uint blocks= -1; + if (keycache->key_cache_inited) + { + if (use_op_lock) + pthread_mutex_lock(&keycache->op_lock); + keycache->interface_funcs->resize(keycache->keycache_cb, + key_cache_block_size, 0, + division_limit, age_threshold, + changed_blocks_hash_size); + end_key_cache_internal(keycache, 1, 0); + blocks= init_key_cache_internal(keycache, key_cache_block_size, use_mem, + division_limit, age_threshold, + changed_blocks_hash_size, partitions, + 0); + if (use_op_lock) + pthread_mutex_unlock(&keycache->op_lock); + } + return blocks; +} + +/* + Repartition a key cache + + SYNOPSIS + repartition_key_cache() + keycache pointer to the key cache to be repartitioned + key_cache_block_size size of blocks to keep cached data + use_mem total memory to use for the new key cache + division_limit new division limit (if not zero) + age_threshold new age threshold (if not zero) + partitions new number of partitions in the key cache + + DESCRIPTION + The function operates over the key cache keycache. + The parameter partitions specifies the number of partitions in the key + cache after repartitioning. If the value of this parameter is 0 then + a simple key cache must be created instead of the old one. + The parameter key_cache_block_size specifies the new size of the block + buffers in the key cache. The parameters division_limit and age_threshold + determine the new initial values of those characteristics of the key cache + that are used for midpoint insertion strategy. The parameter use_mem + specifies the total amount of memory to be allocated for the new key + cache buffers and for all auxiliary structures. + The function calls repartition_key_cache_internal() to perform all these + actions with the last parameter set to TRUE. + + RETURN VALUE + number of blocks in the key cache, if successful, + 0 - otherwise. + + NOTES + Currently the function is called when the value of the variable + key_cache_partitions is being reset for the key cache keycache. +*/ + +int repartition_key_cache(KEY_CACHE *keycache, uint key_cache_block_size, + size_t use_mem, uint division_limit, + uint age_threshold, uint changed_blocks_hash_size, + uint partitions) +{ + return repartition_key_cache_internal(keycache, key_cache_block_size, use_mem, + division_limit, age_threshold, + changed_blocks_hash_size, + partitions, 1); +} + |