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| -rw-r--r-- | src/pcache1.c | 1280 |
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diff --git a/src/pcache1.c b/src/pcache1.c new file mode 100644 index 0000000..adbe953 --- /dev/null +++ b/src/pcache1.c @@ -0,0 +1,1280 @@ +/* +** 2008 November 05 +** +** The author disclaims copyright to this source code. In place of +** a legal notice, here is a blessing: +** +** May you do good and not evil. +** May you find forgiveness for yourself and forgive others. +** May you share freely, never taking more than you give. +** +************************************************************************* +** +** This file implements the default page cache implementation (the +** sqlite3_pcache interface). It also contains part of the implementation +** of the SQLITE_CONFIG_PAGECACHE and sqlite3_release_memory() features. +** If the default page cache implementation is overridden, then neither of +** these two features are available. +** +** A Page cache line looks like this: +** +** ------------------------------------------------------------- +** | database page content | PgHdr1 | MemPage | PgHdr | +** ------------------------------------------------------------- +** +** The database page content is up front (so that buffer overreads tend to +** flow harmlessly into the PgHdr1, MemPage, and PgHdr extensions). MemPage +** is the extension added by the btree.c module containing information such +** as the database page number and how that database page is used. PgHdr +** is added by the pcache.c layer and contains information used to keep track +** of which pages are "dirty". PgHdr1 is an extension added by this +** module (pcache1.c). The PgHdr1 header is a subclass of sqlite3_pcache_page. +** PgHdr1 contains information needed to look up a page by its page number. +** The superclass sqlite3_pcache_page.pBuf points to the start of the +** database page content and sqlite3_pcache_page.pExtra points to PgHdr. +** +** The size of the extension (MemPage+PgHdr+PgHdr1) can be determined at +** runtime using sqlite3_config(SQLITE_CONFIG_PCACHE_HDRSZ, &size). The +** sizes of the extensions sum to 272 bytes on x64 for 3.8.10, but this +** size can vary according to architecture, compile-time options, and +** SQLite library version number. +** +** Historical note: It used to be that if the SQLITE_PCACHE_SEPARATE_HEADER +** was defined, then the page content would be held in a separate memory +** allocation from the PgHdr1. This was intended to avoid clownshoe memory +** allocations. However, the btree layer needs a small (16-byte) overrun +** area after the page content buffer. The header serves as that overrun +** area. Therefore SQLITE_PCACHE_SEPARATE_HEADER was discontinued to avoid +** any possibility of a memory error. +** +** This module tracks pointers to PgHdr1 objects. Only pcache.c communicates +** with this module. Information is passed back and forth as PgHdr1 pointers. +** +** The pcache.c and pager.c modules deal pointers to PgHdr objects. +** The btree.c module deals with pointers to MemPage objects. +** +** SOURCE OF PAGE CACHE MEMORY: +** +** Memory for a page might come from any of three sources: +** +** (1) The general-purpose memory allocator - sqlite3Malloc() +** (2) Global page-cache memory provided using sqlite3_config() with +** SQLITE_CONFIG_PAGECACHE. +** (3) PCache-local bulk allocation. +** +** The third case is a chunk of heap memory (defaulting to 100 pages worth) +** that is allocated when the page cache is created. The size of the local +** bulk allocation can be adjusted using +** +** sqlite3_config(SQLITE_CONFIG_PAGECACHE, (void*)0, 0, N). +** +** If N is positive, then N pages worth of memory are allocated using a single +** sqlite3Malloc() call and that memory is used for the first N pages allocated. +** Or if N is negative, then -1024*N bytes of memory are allocated and used +** for as many pages as can be accomodated. +** +** Only one of (2) or (3) can be used. Once the memory available to (2) or +** (3) is exhausted, subsequent allocations fail over to the general-purpose +** memory allocator (1). +** +** Earlier versions of SQLite used only methods (1) and (2). But experiments +** show that method (3) with N==100 provides about a 5% performance boost for +** common workloads. +*/ +#include "sqliteInt.h" + +typedef struct PCache1 PCache1; +typedef struct PgHdr1 PgHdr1; +typedef struct PgFreeslot PgFreeslot; +typedef struct PGroup PGroup; + +/* +** Each cache entry is represented by an instance of the following +** structure. A buffer of PgHdr1.pCache->szPage bytes is allocated +** directly before this structure and is used to cache the page content. +** +** When reading a corrupt database file, it is possible that SQLite might +** read a few bytes (no more than 16 bytes) past the end of the page buffer. +** It will only read past the end of the page buffer, never write. This +** object is positioned immediately after the page buffer to serve as an +** overrun area, so that overreads are harmless. +** +** Variables isBulkLocal and isAnchor were once type "u8". That works, +** but causes a 2-byte gap in the structure for most architectures (since +** pointers must be either 4 or 8-byte aligned). As this structure is located +** in memory directly after the associated page data, if the database is +** corrupt, code at the b-tree layer may overread the page buffer and +** read part of this structure before the corruption is detected. This +** can cause a valgrind error if the unitialized gap is accessed. Using u16 +** ensures there is no such gap, and therefore no bytes of uninitialized +** memory in the structure. +** +** The pLruNext and pLruPrev pointers form a double-linked circular list +** of all pages that are unpinned. The PGroup.lru element (which should be +** the only element on the list with PgHdr1.isAnchor set to 1) forms the +** beginning and the end of the list. +*/ +struct PgHdr1 { + sqlite3_pcache_page page; /* Base class. Must be first. pBuf & pExtra */ + unsigned int iKey; /* Key value (page number) */ + u16 isBulkLocal; /* This page from bulk local storage */ + u16 isAnchor; /* This is the PGroup.lru element */ + PgHdr1 *pNext; /* Next in hash table chain */ + PCache1 *pCache; /* Cache that currently owns this page */ + PgHdr1 *pLruNext; /* Next in circular LRU list of unpinned pages */ + PgHdr1 *pLruPrev; /* Previous in LRU list of unpinned pages */ + /* NB: pLruPrev is only valid if pLruNext!=0 */ +}; + +/* +** A page is pinned if it is not on the LRU list. To be "pinned" means +** that the page is in active use and must not be deallocated. +*/ +#define PAGE_IS_PINNED(p) ((p)->pLruNext==0) +#define PAGE_IS_UNPINNED(p) ((p)->pLruNext!=0) + +/* Each page cache (or PCache) belongs to a PGroup. A PGroup is a set +** of one or more PCaches that are able to recycle each other's unpinned +** pages when they are under memory pressure. A PGroup is an instance of +** the following object. +** +** This page cache implementation works in one of two modes: +** +** (1) Every PCache is the sole member of its own PGroup. There is +** one PGroup per PCache. +** +** (2) There is a single global PGroup that all PCaches are a member +** of. +** +** Mode 1 uses more memory (since PCache instances are not able to rob +** unused pages from other PCaches) but it also operates without a mutex, +** and is therefore often faster. Mode 2 requires a mutex in order to be +** threadsafe, but recycles pages more efficiently. +** +** For mode (1), PGroup.mutex is NULL. For mode (2) there is only a single +** PGroup which is the pcache1.grp global variable and its mutex is +** SQLITE_MUTEX_STATIC_LRU. +*/ +struct PGroup { + sqlite3_mutex *mutex; /* MUTEX_STATIC_LRU or NULL */ + unsigned int nMaxPage; /* Sum of nMax for purgeable caches */ + unsigned int nMinPage; /* Sum of nMin for purgeable caches */ + unsigned int mxPinned; /* nMaxpage + 10 - nMinPage */ + unsigned int nPurgeable; /* Number of purgeable pages allocated */ + PgHdr1 lru; /* The beginning and end of the LRU list */ +}; + +/* Each page cache is an instance of the following object. Every +** open database file (including each in-memory database and each +** temporary or transient database) has a single page cache which +** is an instance of this object. +** +** Pointers to structures of this type are cast and returned as +** opaque sqlite3_pcache* handles. +*/ +struct PCache1 { + /* Cache configuration parameters. Page size (szPage) and the purgeable + ** flag (bPurgeable) and the pnPurgeable pointer are all set when the + ** cache is created and are never changed thereafter. nMax may be + ** modified at any time by a call to the pcache1Cachesize() method. + ** The PGroup mutex must be held when accessing nMax. + */ + PGroup *pGroup; /* PGroup this cache belongs to */ + unsigned int *pnPurgeable; /* Pointer to pGroup->nPurgeable */ + int szPage; /* Size of database content section */ + int szExtra; /* sizeof(MemPage)+sizeof(PgHdr) */ + int szAlloc; /* Total size of one pcache line */ + int bPurgeable; /* True if cache is purgeable */ + unsigned int nMin; /* Minimum number of pages reserved */ + unsigned int nMax; /* Configured "cache_size" value */ + unsigned int n90pct; /* nMax*9/10 */ + unsigned int iMaxKey; /* Largest key seen since xTruncate() */ + unsigned int nPurgeableDummy; /* pnPurgeable points here when not used*/ + + /* Hash table of all pages. The following variables may only be accessed + ** when the accessor is holding the PGroup mutex. + */ + unsigned int nRecyclable; /* Number of pages in the LRU list */ + unsigned int nPage; /* Total number of pages in apHash */ + unsigned int nHash; /* Number of slots in apHash[] */ + PgHdr1 **apHash; /* Hash table for fast lookup by key */ + PgHdr1 *pFree; /* List of unused pcache-local pages */ + void *pBulk; /* Bulk memory used by pcache-local */ +}; + +/* +** Free slots in the allocator used to divide up the global page cache +** buffer provided using the SQLITE_CONFIG_PAGECACHE mechanism. +*/ +struct PgFreeslot { + PgFreeslot *pNext; /* Next free slot */ +}; + +/* +** Global data used by this cache. +*/ +static SQLITE_WSD struct PCacheGlobal { + PGroup grp; /* The global PGroup for mode (2) */ + + /* Variables related to SQLITE_CONFIG_PAGECACHE settings. The + ** szSlot, nSlot, pStart, pEnd, nReserve, and isInit values are all + ** fixed at sqlite3_initialize() time and do not require mutex protection. + ** The nFreeSlot and pFree values do require mutex protection. + */ + int isInit; /* True if initialized */ + int separateCache; /* Use a new PGroup for each PCache */ + int nInitPage; /* Initial bulk allocation size */ + int szSlot; /* Size of each free slot */ + int nSlot; /* The number of pcache slots */ + int nReserve; /* Try to keep nFreeSlot above this */ + void *pStart, *pEnd; /* Bounds of global page cache memory */ + /* Above requires no mutex. Use mutex below for variable that follow. */ + sqlite3_mutex *mutex; /* Mutex for accessing the following: */ + PgFreeslot *pFree; /* Free page blocks */ + int nFreeSlot; /* Number of unused pcache slots */ + /* The following value requires a mutex to change. We skip the mutex on + ** reading because (1) most platforms read a 32-bit integer atomically and + ** (2) even if an incorrect value is read, no great harm is done since this + ** is really just an optimization. */ + int bUnderPressure; /* True if low on PAGECACHE memory */ +} pcache1_g; + +/* +** All code in this file should access the global structure above via the +** alias "pcache1". This ensures that the WSD emulation is used when +** compiling for systems that do not support real WSD. +*/ +#define pcache1 (GLOBAL(struct PCacheGlobal, pcache1_g)) + +/* +** Macros to enter and leave the PCache LRU mutex. +*/ +#if !defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) || SQLITE_THREADSAFE==0 +# define pcache1EnterMutex(X) assert((X)->mutex==0) +# define pcache1LeaveMutex(X) assert((X)->mutex==0) +# define PCACHE1_MIGHT_USE_GROUP_MUTEX 0 +#else +# define pcache1EnterMutex(X) sqlite3_mutex_enter((X)->mutex) +# define pcache1LeaveMutex(X) sqlite3_mutex_leave((X)->mutex) +# define PCACHE1_MIGHT_USE_GROUP_MUTEX 1 +#endif + +/******************************************************************************/ +/******** Page Allocation/SQLITE_CONFIG_PCACHE Related Functions **************/ + + +/* +** This function is called during initialization if a static buffer is +** supplied to use for the page-cache by passing the SQLITE_CONFIG_PAGECACHE +** verb to sqlite3_config(). Parameter pBuf points to an allocation large +** enough to contain 'n' buffers of 'sz' bytes each. +** +** This routine is called from sqlite3_initialize() and so it is guaranteed +** to be serialized already. There is no need for further mutexing. +*/ +void sqlite3PCacheBufferSetup(void *pBuf, int sz, int n){ + if( pcache1.isInit ){ + PgFreeslot *p; + if( pBuf==0 ) sz = n = 0; + if( n==0 ) sz = 0; + sz = ROUNDDOWN8(sz); + pcache1.szSlot = sz; + pcache1.nSlot = pcache1.nFreeSlot = n; + pcache1.nReserve = n>90 ? 10 : (n/10 + 1); + pcache1.pStart = pBuf; + pcache1.pFree = 0; + pcache1.bUnderPressure = 0; + while( n-- ){ + p = (PgFreeslot*)pBuf; + p->pNext = pcache1.pFree; + pcache1.pFree = p; + pBuf = (void*)&((char*)pBuf)[sz]; + } + pcache1.pEnd = pBuf; + } +} + +/* +** Try to initialize the pCache->pFree and pCache->pBulk fields. Return +** true if pCache->pFree ends up containing one or more free pages. +*/ +static int pcache1InitBulk(PCache1 *pCache){ + i64 szBulk; + char *zBulk; + if( pcache1.nInitPage==0 ) return 0; + /* Do not bother with a bulk allocation if the cache size very small */ + if( pCache->nMax<3 ) return 0; + sqlite3BeginBenignMalloc(); + if( pcache1.nInitPage>0 ){ + szBulk = pCache->szAlloc * (i64)pcache1.nInitPage; + }else{ + szBulk = -1024 * (i64)pcache1.nInitPage; + } + if( szBulk > pCache->szAlloc*(i64)pCache->nMax ){ + szBulk = pCache->szAlloc*(i64)pCache->nMax; + } + zBulk = pCache->pBulk = sqlite3Malloc( szBulk ); + sqlite3EndBenignMalloc(); + if( zBulk ){ + int nBulk = sqlite3MallocSize(zBulk)/pCache->szAlloc; + do{ + PgHdr1 *pX = (PgHdr1*)&zBulk[pCache->szPage]; + pX->page.pBuf = zBulk; + pX->page.pExtra = &pX[1]; + pX->isBulkLocal = 1; + pX->isAnchor = 0; + pX->pNext = pCache->pFree; + pX->pLruPrev = 0; /* Initializing this saves a valgrind error */ + pCache->pFree = pX; + zBulk += pCache->szAlloc; + }while( --nBulk ); + } + return pCache->pFree!=0; +} + +/* +** Malloc function used within this file to allocate space from the buffer +** configured using sqlite3_config(SQLITE_CONFIG_PAGECACHE) option. If no +** such buffer exists or there is no space left in it, this function falls +** back to sqlite3Malloc(). +** +** Multiple threads can run this routine at the same time. Global variables +** in pcache1 need to be protected via mutex. +*/ +static void *pcache1Alloc(int nByte){ + void *p = 0; + assert( sqlite3_mutex_notheld(pcache1.grp.mutex) ); + if( nByte<=pcache1.szSlot ){ + sqlite3_mutex_enter(pcache1.mutex); + p = (PgHdr1 *)pcache1.pFree; + if( p ){ + pcache1.pFree = pcache1.pFree->pNext; + pcache1.nFreeSlot--; + pcache1.bUnderPressure = pcache1.nFreeSlot<pcache1.nReserve; + assert( pcache1.nFreeSlot>=0 ); + sqlite3StatusHighwater(SQLITE_STATUS_PAGECACHE_SIZE, nByte); + sqlite3StatusUp(SQLITE_STATUS_PAGECACHE_USED, 1); + } + sqlite3_mutex_leave(pcache1.mutex); + } + if( p==0 ){ + /* Memory is not available in the SQLITE_CONFIG_PAGECACHE pool. Get + ** it from sqlite3Malloc instead. + */ + p = sqlite3Malloc(nByte); +#ifndef SQLITE_DISABLE_PAGECACHE_OVERFLOW_STATS + if( p ){ + int sz = sqlite3MallocSize(p); + sqlite3_mutex_enter(pcache1.mutex); + sqlite3StatusHighwater(SQLITE_STATUS_PAGECACHE_SIZE, nByte); + sqlite3StatusUp(SQLITE_STATUS_PAGECACHE_OVERFLOW, sz); + sqlite3_mutex_leave(pcache1.mutex); + } +#endif + sqlite3MemdebugSetType(p, MEMTYPE_PCACHE); + } + return p; +} + +/* +** Free an allocated buffer obtained from pcache1Alloc(). +*/ +static void pcache1Free(void *p){ + if( p==0 ) return; + if( SQLITE_WITHIN(p, pcache1.pStart, pcache1.pEnd) ){ + PgFreeslot *pSlot; + sqlite3_mutex_enter(pcache1.mutex); + sqlite3StatusDown(SQLITE_STATUS_PAGECACHE_USED, 1); + pSlot = (PgFreeslot*)p; + pSlot->pNext = pcache1.pFree; + pcache1.pFree = pSlot; + pcache1.nFreeSlot++; + pcache1.bUnderPressure = pcache1.nFreeSlot<pcache1.nReserve; + assert( pcache1.nFreeSlot<=pcache1.nSlot ); + sqlite3_mutex_leave(pcache1.mutex); + }else{ + assert( sqlite3MemdebugHasType(p, MEMTYPE_PCACHE) ); + sqlite3MemdebugSetType(p, MEMTYPE_HEAP); +#ifndef SQLITE_DISABLE_PAGECACHE_OVERFLOW_STATS + { + int nFreed = 0; + nFreed = sqlite3MallocSize(p); + sqlite3_mutex_enter(pcache1.mutex); + sqlite3StatusDown(SQLITE_STATUS_PAGECACHE_OVERFLOW, nFreed); + sqlite3_mutex_leave(pcache1.mutex); + } +#endif + sqlite3_free(p); + } +} + +#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT +/* +** Return the size of a pcache allocation +*/ +static int pcache1MemSize(void *p){ + if( p>=pcache1.pStart && p<pcache1.pEnd ){ + return pcache1.szSlot; + }else{ + int iSize; + assert( sqlite3MemdebugHasType(p, MEMTYPE_PCACHE) ); + sqlite3MemdebugSetType(p, MEMTYPE_HEAP); + iSize = sqlite3MallocSize(p); + sqlite3MemdebugSetType(p, MEMTYPE_PCACHE); + return iSize; + } +} +#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */ + +/* +** Allocate a new page object initially associated with cache pCache. +*/ +static PgHdr1 *pcache1AllocPage(PCache1 *pCache, int benignMalloc){ + PgHdr1 *p = 0; + void *pPg; + + assert( sqlite3_mutex_held(pCache->pGroup->mutex) ); + if( pCache->pFree || (pCache->nPage==0 && pcache1InitBulk(pCache)) ){ + assert( pCache->pFree!=0 ); + p = pCache->pFree; + pCache->pFree = p->pNext; + p->pNext = 0; + }else{ +#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT + /* The group mutex must be released before pcache1Alloc() is called. This + ** is because it might call sqlite3_release_memory(), which assumes that + ** this mutex is not held. */ + assert( pcache1.separateCache==0 ); + assert( pCache->pGroup==&pcache1.grp ); + pcache1LeaveMutex(pCache->pGroup); +#endif + if( benignMalloc ){ sqlite3BeginBenignMalloc(); } + pPg = pcache1Alloc(pCache->szAlloc); + if( benignMalloc ){ sqlite3EndBenignMalloc(); } +#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT + pcache1EnterMutex(pCache->pGroup); +#endif + if( pPg==0 ) return 0; + p = (PgHdr1 *)&((u8 *)pPg)[pCache->szPage]; + p->page.pBuf = pPg; + p->page.pExtra = &p[1]; + p->isBulkLocal = 0; + p->isAnchor = 0; + p->pLruPrev = 0; /* Initializing this saves a valgrind error */ + } + (*pCache->pnPurgeable)++; + return p; +} + +/* +** Free a page object allocated by pcache1AllocPage(). +*/ +static void pcache1FreePage(PgHdr1 *p){ + PCache1 *pCache; + assert( p!=0 ); + pCache = p->pCache; + assert( sqlite3_mutex_held(p->pCache->pGroup->mutex) ); + if( p->isBulkLocal ){ + p->pNext = pCache->pFree; + pCache->pFree = p; + }else{ + pcache1Free(p->page.pBuf); + } + (*pCache->pnPurgeable)--; +} + +/* +** Malloc function used by SQLite to obtain space from the buffer configured +** using sqlite3_config(SQLITE_CONFIG_PAGECACHE) option. If no such buffer +** exists, this function falls back to sqlite3Malloc(). +*/ +void *sqlite3PageMalloc(int sz){ + assert( sz<=65536+8 ); /* These allocations are never very large */ + return pcache1Alloc(sz); +} + +/* +** Free an allocated buffer obtained from sqlite3PageMalloc(). +*/ +void sqlite3PageFree(void *p){ + pcache1Free(p); +} + + +/* +** Return true if it desirable to avoid allocating a new page cache +** entry. +** +** If memory was allocated specifically to the page cache using +** SQLITE_CONFIG_PAGECACHE but that memory has all been used, then +** it is desirable to avoid allocating a new page cache entry because +** presumably SQLITE_CONFIG_PAGECACHE was suppose to be sufficient +** for all page cache needs and we should not need to spill the +** allocation onto the heap. +** +** Or, the heap is used for all page cache memory but the heap is +** under memory pressure, then again it is desirable to avoid +** allocating a new page cache entry in order to avoid stressing +** the heap even further. +*/ +static int pcache1UnderMemoryPressure(PCache1 *pCache){ + if( pcache1.nSlot && (pCache->szPage+pCache->szExtra)<=pcache1.szSlot ){ + return pcache1.bUnderPressure; + }else{ + return sqlite3HeapNearlyFull(); + } +} + +/******************************************************************************/ +/******** General Implementation Functions ************************************/ + +/* +** This function is used to resize the hash table used by the cache passed +** as the first argument. +** +** The PCache mutex must be held when this function is called. +*/ +static void pcache1ResizeHash(PCache1 *p){ + PgHdr1 **apNew; + unsigned int nNew; + unsigned int i; + + assert( sqlite3_mutex_held(p->pGroup->mutex) ); + + nNew = p->nHash*2; + if( nNew<256 ){ + nNew = 256; + } + + pcache1LeaveMutex(p->pGroup); + if( p->nHash ){ sqlite3BeginBenignMalloc(); } + apNew = (PgHdr1 **)sqlite3MallocZero(sizeof(PgHdr1 *)*nNew); + if( p->nHash ){ sqlite3EndBenignMalloc(); } + pcache1EnterMutex(p->pGroup); + if( apNew ){ + for(i=0; i<p->nHash; i++){ + PgHdr1 *pPage; + PgHdr1 *pNext = p->apHash[i]; + while( (pPage = pNext)!=0 ){ + unsigned int h = pPage->iKey % nNew; + pNext = pPage->pNext; + pPage->pNext = apNew[h]; + apNew[h] = pPage; + } + } + sqlite3_free(p->apHash); + p->apHash = apNew; + p->nHash = nNew; + } +} + +/* +** This function is used internally to remove the page pPage from the +** PGroup LRU list, if is part of it. If pPage is not part of the PGroup +** LRU list, then this function is a no-op. +** +** The PGroup mutex must be held when this function is called. +*/ +static PgHdr1 *pcache1PinPage(PgHdr1 *pPage){ + assert( pPage!=0 ); + assert( PAGE_IS_UNPINNED(pPage) ); + assert( pPage->pLruNext ); + assert( pPage->pLruPrev ); + assert( sqlite3_mutex_held(pPage->pCache->pGroup->mutex) ); + pPage->pLruPrev->pLruNext = pPage->pLruNext; + pPage->pLruNext->pLruPrev = pPage->pLruPrev; + pPage->pLruNext = 0; + /* pPage->pLruPrev = 0; + ** No need to clear pLruPrev as it is never accessed if pLruNext is 0 */ + assert( pPage->isAnchor==0 ); + assert( pPage->pCache->pGroup->lru.isAnchor==1 ); + pPage->pCache->nRecyclable--; + return pPage; +} + + +/* +** Remove the page supplied as an argument from the hash table +** (PCache1.apHash structure) that it is currently stored in. +** Also free the page if freePage is true. +** +** The PGroup mutex must be held when this function is called. +*/ +static void pcache1RemoveFromHash(PgHdr1 *pPage, int freeFlag){ + unsigned int h; + PCache1 *pCache = pPage->pCache; + PgHdr1 **pp; + + assert( sqlite3_mutex_held(pCache->pGroup->mutex) ); + h = pPage->iKey % pCache->nHash; + for(pp=&pCache->apHash[h]; (*pp)!=pPage; pp=&(*pp)->pNext); + *pp = (*pp)->pNext; + + pCache->nPage--; + if( freeFlag ) pcache1FreePage(pPage); +} + +/* +** If there are currently more than nMaxPage pages allocated, try +** to recycle pages to reduce the number allocated to nMaxPage. +*/ +static void pcache1EnforceMaxPage(PCache1 *pCache){ + PGroup *pGroup = pCache->pGroup; + PgHdr1 *p; + assert( sqlite3_mutex_held(pGroup->mutex) ); + while( pGroup->nPurgeable>pGroup->nMaxPage + && (p=pGroup->lru.pLruPrev)->isAnchor==0 + ){ + assert( p->pCache->pGroup==pGroup ); + assert( PAGE_IS_UNPINNED(p) ); + pcache1PinPage(p); + pcache1RemoveFromHash(p, 1); + } + if( pCache->nPage==0 && pCache->pBulk ){ + sqlite3_free(pCache->pBulk); + pCache->pBulk = pCache->pFree = 0; + } +} + +/* +** Discard all pages from cache pCache with a page number (key value) +** greater than or equal to iLimit. Any pinned pages that meet this +** criteria are unpinned before they are discarded. +** +** The PCache mutex must be held when this function is called. +*/ +static void pcache1TruncateUnsafe( + PCache1 *pCache, /* The cache to truncate */ + unsigned int iLimit /* Drop pages with this pgno or larger */ +){ + TESTONLY( int nPage = 0; ) /* To assert pCache->nPage is correct */ + unsigned int h, iStop; + assert( sqlite3_mutex_held(pCache->pGroup->mutex) ); + assert( pCache->iMaxKey >= iLimit ); + assert( pCache->nHash > 0 ); + if( pCache->iMaxKey - iLimit < pCache->nHash ){ + /* If we are just shaving the last few pages off the end of the + ** cache, then there is no point in scanning the entire hash table. + ** Only scan those hash slots that might contain pages that need to + ** be removed. */ + h = iLimit % pCache->nHash; + iStop = pCache->iMaxKey % pCache->nHash; + TESTONLY( nPage = -10; ) /* Disable the pCache->nPage validity check */ + }else{ + /* This is the general case where many pages are being removed. + ** It is necessary to scan the entire hash table */ + h = pCache->nHash/2; + iStop = h - 1; + } + for(;;){ + PgHdr1 **pp; + PgHdr1 *pPage; + assert( h<pCache->nHash ); + pp = &pCache->apHash[h]; + while( (pPage = *pp)!=0 ){ + if( pPage->iKey>=iLimit ){ + pCache->nPage--; + *pp = pPage->pNext; + if( PAGE_IS_UNPINNED(pPage) ) pcache1PinPage(pPage); + pcache1FreePage(pPage); + }else{ + pp = &pPage->pNext; + TESTONLY( if( nPage>=0 ) nPage++; ) + } + } + if( h==iStop ) break; + h = (h+1) % pCache->nHash; + } + assert( nPage<0 || pCache->nPage==(unsigned)nPage ); +} + +/******************************************************************************/ +/******** sqlite3_pcache Methods **********************************************/ + +/* +** Implementation of the sqlite3_pcache.xInit method. +*/ +static int pcache1Init(void *NotUsed){ + UNUSED_PARAMETER(NotUsed); + assert( pcache1.isInit==0 ); + memset(&pcache1, 0, sizeof(pcache1)); + + + /* + ** The pcache1.separateCache variable is true if each PCache has its own + ** private PGroup (mode-1). pcache1.separateCache is false if the single + ** PGroup in pcache1.grp is used for all page caches (mode-2). + ** + ** * Always use a unified cache (mode-2) if ENABLE_MEMORY_MANAGEMENT + ** + ** * Use a unified cache in single-threaded applications that have + ** configured a start-time buffer for use as page-cache memory using + ** sqlite3_config(SQLITE_CONFIG_PAGECACHE, pBuf, sz, N) with non-NULL + ** pBuf argument. + ** + ** * Otherwise use separate caches (mode-1) + */ +#if defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) + pcache1.separateCache = 0; +#elif SQLITE_THREADSAFE + pcache1.separateCache = sqlite3GlobalConfig.pPage==0 + || sqlite3GlobalConfig.bCoreMutex>0; +#else + pcache1.separateCache = sqlite3GlobalConfig.pPage==0; +#endif + +#if SQLITE_THREADSAFE + if( sqlite3GlobalConfig.bCoreMutex ){ + pcache1.grp.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_LRU); + pcache1.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_PMEM); + } +#endif + if( pcache1.separateCache + && sqlite3GlobalConfig.nPage!=0 + && sqlite3GlobalConfig.pPage==0 + ){ + pcache1.nInitPage = sqlite3GlobalConfig.nPage; + }else{ + pcache1.nInitPage = 0; + } + pcache1.grp.mxPinned = 10; + pcache1.isInit = 1; + return SQLITE_OK; +} + +/* +** Implementation of the sqlite3_pcache.xShutdown method. +** Note that the static mutex allocated in xInit does +** not need to be freed. +*/ +static void pcache1Shutdown(void *NotUsed){ + UNUSED_PARAMETER(NotUsed); + assert( pcache1.isInit!=0 ); + memset(&pcache1, 0, sizeof(pcache1)); +} + +/* forward declaration */ +static void pcache1Destroy(sqlite3_pcache *p); + +/* +** Implementation of the sqlite3_pcache.xCreate method. +** +** Allocate a new cache. +*/ +static sqlite3_pcache *pcache1Create(int szPage, int szExtra, int bPurgeable){ + PCache1 *pCache; /* The newly created page cache */ + PGroup *pGroup; /* The group the new page cache will belong to */ + int sz; /* Bytes of memory required to allocate the new cache */ + + assert( (szPage & (szPage-1))==0 && szPage>=512 && szPage<=65536 ); + assert( szExtra < 300 ); + + sz = sizeof(PCache1) + sizeof(PGroup)*pcache1.separateCache; + pCache = (PCache1 *)sqlite3MallocZero(sz); + if( pCache ){ + if( pcache1.separateCache ){ + pGroup = (PGroup*)&pCache[1]; + pGroup->mxPinned = 10; + }else{ + pGroup = &pcache1.grp; + } + pcache1EnterMutex(pGroup); + if( pGroup->lru.isAnchor==0 ){ + pGroup->lru.isAnchor = 1; + pGroup->lru.pLruPrev = pGroup->lru.pLruNext = &pGroup->lru; + } + pCache->pGroup = pGroup; + pCache->szPage = szPage; + pCache->szExtra = szExtra; + pCache->szAlloc = szPage + szExtra + ROUND8(sizeof(PgHdr1)); + pCache->bPurgeable = (bPurgeable ? 1 : 0); + pcache1ResizeHash(pCache); + if( bPurgeable ){ + pCache->nMin = 10; + pGroup->nMinPage += pCache->nMin; + pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage; + pCache->pnPurgeable = &pGroup->nPurgeable; + }else{ + pCache->pnPurgeable = &pCache->nPurgeableDummy; + } + pcache1LeaveMutex(pGroup); + if( pCache->nHash==0 ){ + pcache1Destroy((sqlite3_pcache*)pCache); + pCache = 0; + } + } + return (sqlite3_pcache *)pCache; +} + +/* +** Implementation of the sqlite3_pcache.xCachesize method. +** +** Configure the cache_size limit for a cache. +*/ +static void pcache1Cachesize(sqlite3_pcache *p, int nMax){ + PCache1 *pCache = (PCache1 *)p; + u32 n; + assert( nMax>=0 ); + if( pCache->bPurgeable ){ + PGroup *pGroup = pCache->pGroup; + pcache1EnterMutex(pGroup); + n = (u32)nMax; + if( n > 0x7fff0000 - pGroup->nMaxPage + pCache->nMax ){ + n = 0x7fff0000 - pGroup->nMaxPage + pCache->nMax; + } + pGroup->nMaxPage += (n - pCache->nMax); + pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage; + pCache->nMax = n; + pCache->n90pct = pCache->nMax*9/10; + pcache1EnforceMaxPage(pCache); + pcache1LeaveMutex(pGroup); + } +} + +/* +** Implementation of the sqlite3_pcache.xShrink method. +** +** Free up as much memory as possible. +*/ +static void pcache1Shrink(sqlite3_pcache *p){ + PCache1 *pCache = (PCache1*)p; + if( pCache->bPurgeable ){ + PGroup *pGroup = pCache->pGroup; + unsigned int savedMaxPage; + pcache1EnterMutex(pGroup); + savedMaxPage = pGroup->nMaxPage; + pGroup->nMaxPage = 0; + pcache1EnforceMaxPage(pCache); + pGroup->nMaxPage = savedMaxPage; + pcache1LeaveMutex(pGroup); + } +} + +/* +** Implementation of the sqlite3_pcache.xPagecount method. +*/ +static int pcache1Pagecount(sqlite3_pcache *p){ + int n; + PCache1 *pCache = (PCache1*)p; + pcache1EnterMutex(pCache->pGroup); + n = pCache->nPage; + pcache1LeaveMutex(pCache->pGroup); + return n; +} + + +/* +** Implement steps 3, 4, and 5 of the pcache1Fetch() algorithm described +** in the header of the pcache1Fetch() procedure. +** +** This steps are broken out into a separate procedure because they are +** usually not needed, and by avoiding the stack initialization required +** for these steps, the main pcache1Fetch() procedure can run faster. +*/ +static SQLITE_NOINLINE PgHdr1 *pcache1FetchStage2( + PCache1 *pCache, + unsigned int iKey, + int createFlag +){ + unsigned int nPinned; + PGroup *pGroup = pCache->pGroup; + PgHdr1 *pPage = 0; + + /* Step 3: Abort if createFlag is 1 but the cache is nearly full */ + assert( pCache->nPage >= pCache->nRecyclable ); + nPinned = pCache->nPage - pCache->nRecyclable; + assert( pGroup->mxPinned == pGroup->nMaxPage + 10 - pGroup->nMinPage ); + assert( pCache->n90pct == pCache->nMax*9/10 ); + if( createFlag==1 && ( + nPinned>=pGroup->mxPinned + || nPinned>=pCache->n90pct + || (pcache1UnderMemoryPressure(pCache) && pCache->nRecyclable<nPinned) + )){ + return 0; + } + + if( pCache->nPage>=pCache->nHash ) pcache1ResizeHash(pCache); + assert( pCache->nHash>0 && pCache->apHash ); + + /* Step 4. Try to recycle a page. */ + if( pCache->bPurgeable + && !pGroup->lru.pLruPrev->isAnchor + && ((pCache->nPage+1>=pCache->nMax) || pcache1UnderMemoryPressure(pCache)) + ){ + PCache1 *pOther; + pPage = pGroup->lru.pLruPrev; + assert( PAGE_IS_UNPINNED(pPage) ); + pcache1RemoveFromHash(pPage, 0); + pcache1PinPage(pPage); + pOther = pPage->pCache; + if( pOther->szAlloc != pCache->szAlloc ){ + pcache1FreePage(pPage); + pPage = 0; + }else{ + pGroup->nPurgeable -= (pOther->bPurgeable - pCache->bPurgeable); + } + } + + /* Step 5. If a usable page buffer has still not been found, + ** attempt to allocate a new one. + */ + if( !pPage ){ + pPage = pcache1AllocPage(pCache, createFlag==1); + } + + if( pPage ){ + unsigned int h = iKey % pCache->nHash; + pCache->nPage++; + pPage->iKey = iKey; + pPage->pNext = pCache->apHash[h]; + pPage->pCache = pCache; + pPage->pLruNext = 0; + /* pPage->pLruPrev = 0; + ** No need to clear pLruPrev since it is not accessed when pLruNext==0 */ + *(void **)pPage->page.pExtra = 0; + pCache->apHash[h] = pPage; + if( iKey>pCache->iMaxKey ){ + pCache->iMaxKey = iKey; + } + } + return pPage; +} + +/* +** Implementation of the sqlite3_pcache.xFetch method. +** +** Fetch a page by key value. +** +** Whether or not a new page may be allocated by this function depends on +** the value of the createFlag argument. 0 means do not allocate a new +** page. 1 means allocate a new page if space is easily available. 2 +** means to try really hard to allocate a new page. +** +** For a non-purgeable cache (a cache used as the storage for an in-memory +** database) there is really no difference between createFlag 1 and 2. So +** the calling function (pcache.c) will never have a createFlag of 1 on +** a non-purgeable cache. +** +** There are three different approaches to obtaining space for a page, +** depending on the value of parameter createFlag (which may be 0, 1 or 2). +** +** 1. Regardless of the value of createFlag, the cache is searched for a +** copy of the requested page. If one is found, it is returned. +** +** 2. If createFlag==0 and the page is not already in the cache, NULL is +** returned. +** +** 3. If createFlag is 1, and the page is not already in the cache, then +** return NULL (do not allocate a new page) if any of the following +** conditions are true: +** +** (a) the number of pages pinned by the cache is greater than +** PCache1.nMax, or +** +** (b) the number of pages pinned by the cache is greater than +** the sum of nMax for all purgeable caches, less the sum of +** nMin for all other purgeable caches, or +** +** 4. If none of the first three conditions apply and the cache is marked +** as purgeable, and if one of the following is true: +** +** (a) The number of pages allocated for the cache is already +** PCache1.nMax, or +** +** (b) The number of pages allocated for all purgeable caches is +** already equal to or greater than the sum of nMax for all +** purgeable caches, +** +** (c) The system is under memory pressure and wants to avoid +** unnecessary pages cache entry allocations +** +** then attempt to recycle a page from the LRU list. If it is the right +** size, return the recycled buffer. Otherwise, free the buffer and +** proceed to step 5. +** +** 5. Otherwise, allocate and return a new page buffer. +** +** There are two versions of this routine. pcache1FetchWithMutex() is +** the general case. pcache1FetchNoMutex() is a faster implementation for +** the common case where pGroup->mutex is NULL. The pcache1Fetch() wrapper +** invokes the appropriate routine. +*/ +static PgHdr1 *pcache1FetchNoMutex( + sqlite3_pcache *p, + unsigned int iKey, + int createFlag +){ + PCache1 *pCache = (PCache1 *)p; + PgHdr1 *pPage = 0; + + /* Step 1: Search the hash table for an existing entry. */ + pPage = pCache->apHash[iKey % pCache->nHash]; + while( pPage && pPage->iKey!=iKey ){ pPage = pPage->pNext; } + + /* Step 2: If the page was found in the hash table, then return it. + ** If the page was not in the hash table and createFlag is 0, abort. + ** Otherwise (page not in hash and createFlag!=0) continue with + ** subsequent steps to try to create the page. */ + if( pPage ){ + if( PAGE_IS_UNPINNED(pPage) ){ + return pcache1PinPage(pPage); + }else{ + return pPage; + } + }else if( createFlag ){ + /* Steps 3, 4, and 5 implemented by this subroutine */ + return pcache1FetchStage2(pCache, iKey, createFlag); + }else{ + return 0; + } +} +#if PCACHE1_MIGHT_USE_GROUP_MUTEX +static PgHdr1 *pcache1FetchWithMutex( + sqlite3_pcache *p, + unsigned int iKey, + int createFlag +){ + PCache1 *pCache = (PCache1 *)p; + PgHdr1 *pPage; + + pcache1EnterMutex(pCache->pGroup); + pPage = pcache1FetchNoMutex(p, iKey, createFlag); + assert( pPage==0 || pCache->iMaxKey>=iKey ); + pcache1LeaveMutex(pCache->pGroup); + return pPage; +} +#endif +static sqlite3_pcache_page *pcache1Fetch( + sqlite3_pcache *p, + unsigned int iKey, + int createFlag +){ +#if PCACHE1_MIGHT_USE_GROUP_MUTEX || defined(SQLITE_DEBUG) + PCache1 *pCache = (PCache1 *)p; +#endif + + assert( offsetof(PgHdr1,page)==0 ); + assert( pCache->bPurgeable || createFlag!=1 ); + assert( pCache->bPurgeable || pCache->nMin==0 ); + assert( pCache->bPurgeable==0 || pCache->nMin==10 ); + assert( pCache->nMin==0 || pCache->bPurgeable ); + assert( pCache->nHash>0 ); +#if PCACHE1_MIGHT_USE_GROUP_MUTEX + if( pCache->pGroup->mutex ){ + return (sqlite3_pcache_page*)pcache1FetchWithMutex(p, iKey, createFlag); + }else +#endif + { + return (sqlite3_pcache_page*)pcache1FetchNoMutex(p, iKey, createFlag); + } +} + + +/* +** Implementation of the sqlite3_pcache.xUnpin method. +** +** Mark a page as unpinned (eligible for asynchronous recycling). +*/ +static void pcache1Unpin( + sqlite3_pcache *p, + sqlite3_pcache_page *pPg, + int reuseUnlikely +){ + PCache1 *pCache = (PCache1 *)p; + PgHdr1 *pPage = (PgHdr1 *)pPg; + PGroup *pGroup = pCache->pGroup; + + assert( pPage->pCache==pCache ); + pcache1EnterMutex(pGroup); + + /* It is an error to call this function if the page is already + ** part of the PGroup LRU list. + */ + assert( pPage->pLruNext==0 ); + assert( PAGE_IS_PINNED(pPage) ); + + if( reuseUnlikely || pGroup->nPurgeable>pGroup->nMaxPage ){ + pcache1RemoveFromHash(pPage, 1); + }else{ + /* Add the page to the PGroup LRU list. */ + PgHdr1 **ppFirst = &pGroup->lru.pLruNext; + pPage->pLruPrev = &pGroup->lru; + (pPage->pLruNext = *ppFirst)->pLruPrev = pPage; + *ppFirst = pPage; + pCache->nRecyclable++; + } + + pcache1LeaveMutex(pCache->pGroup); +} + +/* +** Implementation of the sqlite3_pcache.xRekey method. +*/ +static void pcache1Rekey( + sqlite3_pcache *p, + sqlite3_pcache_page *pPg, + unsigned int iOld, + unsigned int iNew +){ + PCache1 *pCache = (PCache1 *)p; + PgHdr1 *pPage = (PgHdr1 *)pPg; + PgHdr1 **pp; + unsigned int hOld, hNew; + assert( pPage->iKey==iOld ); + assert( pPage->pCache==pCache ); + assert( iOld!=iNew ); /* The page number really is changing */ + + pcache1EnterMutex(pCache->pGroup); + + assert( pcache1FetchNoMutex(p, iOld, 0)==pPage ); /* pPg really is iOld */ + hOld = iOld%pCache->nHash; + pp = &pCache->apHash[hOld]; + while( (*pp)!=pPage ){ + pp = &(*pp)->pNext; + } + *pp = pPage->pNext; + + assert( pcache1FetchNoMutex(p, iNew, 0)==0 ); /* iNew not in cache */ + hNew = iNew%pCache->nHash; + pPage->iKey = iNew; + pPage->pNext = pCache->apHash[hNew]; + pCache->apHash[hNew] = pPage; + if( iNew>pCache->iMaxKey ){ + pCache->iMaxKey = iNew; + } + + pcache1LeaveMutex(pCache->pGroup); +} + +/* +** Implementation of the sqlite3_pcache.xTruncate method. +** +** Discard all unpinned pages in the cache with a page number equal to +** or greater than parameter iLimit. Any pinned pages with a page number +** equal to or greater than iLimit are implicitly unpinned. +*/ +static void pcache1Truncate(sqlite3_pcache *p, unsigned int iLimit){ + PCache1 *pCache = (PCache1 *)p; + pcache1EnterMutex(pCache->pGroup); + if( iLimit<=pCache->iMaxKey ){ + pcache1TruncateUnsafe(pCache, iLimit); + pCache->iMaxKey = iLimit-1; + } + pcache1LeaveMutex(pCache->pGroup); +} + +/* +** Implementation of the sqlite3_pcache.xDestroy method. +** +** Destroy a cache allocated using pcache1Create(). +*/ +static void pcache1Destroy(sqlite3_pcache *p){ + PCache1 *pCache = (PCache1 *)p; + PGroup *pGroup = pCache->pGroup; + assert( pCache->bPurgeable || (pCache->nMax==0 && pCache->nMin==0) ); + pcache1EnterMutex(pGroup); + if( pCache->nPage ) pcache1TruncateUnsafe(pCache, 0); + assert( pGroup->nMaxPage >= pCache->nMax ); + pGroup->nMaxPage -= pCache->nMax; + assert( pGroup->nMinPage >= pCache->nMin ); + pGroup->nMinPage -= pCache->nMin; + pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage; + pcache1EnforceMaxPage(pCache); + pcache1LeaveMutex(pGroup); + sqlite3_free(pCache->pBulk); + sqlite3_free(pCache->apHash); + sqlite3_free(pCache); +} + +/* +** This function is called during initialization (sqlite3_initialize()) to +** install the default pluggable cache module, assuming the user has not +** already provided an alternative. +*/ +void sqlite3PCacheSetDefault(void){ + static const sqlite3_pcache_methods2 defaultMethods = { + 1, /* iVersion */ + 0, /* pArg */ + pcache1Init, /* xInit */ + pcache1Shutdown, /* xShutdown */ + pcache1Create, /* xCreate */ + pcache1Cachesize, /* xCachesize */ + pcache1Pagecount, /* xPagecount */ + pcache1Fetch, /* xFetch */ + pcache1Unpin, /* xUnpin */ + pcache1Rekey, /* xRekey */ + pcache1Truncate, /* xTruncate */ + pcache1Destroy, /* xDestroy */ + pcache1Shrink /* xShrink */ + }; + sqlite3_config(SQLITE_CONFIG_PCACHE2, &defaultMethods); +} + +/* +** Return the size of the header on each page of this PCACHE implementation. +*/ +int sqlite3HeaderSizePcache1(void){ return ROUND8(sizeof(PgHdr1)); } + +/* +** Return the global mutex used by this PCACHE implementation. The +** sqlite3_status() routine needs access to this mutex. +*/ +sqlite3_mutex *sqlite3Pcache1Mutex(void){ + return pcache1.mutex; +} + +#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT +/* +** This function is called to free superfluous dynamically allocated memory +** held by the pager system. Memory in use by any SQLite pager allocated +** by the current thread may be sqlite3_free()ed. +** +** nReq is the number of bytes of memory required. Once this much has +** been released, the function returns. The return value is the total number +** of bytes of memory released. +*/ +int sqlite3PcacheReleaseMemory(int nReq){ + int nFree = 0; + assert( sqlite3_mutex_notheld(pcache1.grp.mutex) ); + assert( sqlite3_mutex_notheld(pcache1.mutex) ); + if( sqlite3GlobalConfig.pPage==0 ){ + PgHdr1 *p; + pcache1EnterMutex(&pcache1.grp); + while( (nReq<0 || nFree<nReq) + && (p=pcache1.grp.lru.pLruPrev)!=0 + && p->isAnchor==0 + ){ + nFree += pcache1MemSize(p->page.pBuf); + assert( PAGE_IS_UNPINNED(p) ); + pcache1PinPage(p); + pcache1RemoveFromHash(p, 1); + } + pcache1LeaveMutex(&pcache1.grp); + } + return nFree; +} +#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */ + +#ifdef SQLITE_TEST +/* +** This function is used by test procedures to inspect the internal state +** of the global cache. +*/ +void sqlite3PcacheStats( + int *pnCurrent, /* OUT: Total number of pages cached */ + int *pnMax, /* OUT: Global maximum cache size */ + int *pnMin, /* OUT: Sum of PCache1.nMin for purgeable caches */ + int *pnRecyclable /* OUT: Total number of pages available for recycling */ +){ + PgHdr1 *p; + int nRecyclable = 0; + for(p=pcache1.grp.lru.pLruNext; p && !p->isAnchor; p=p->pLruNext){ + assert( PAGE_IS_UNPINNED(p) ); + nRecyclable++; + } + *pnCurrent = pcache1.grp.nPurgeable; + *pnMax = (int)pcache1.grp.nMaxPage; + *pnMin = (int)pcache1.grp.nMinPage; + *pnRecyclable = nRecyclable; +} +#endif |