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Diffstat (limited to 'src/pcache.c')
| -rw-r--r-- | src/pcache.c | 922 |
1 files changed, 922 insertions, 0 deletions
diff --git a/src/pcache.c b/src/pcache.c new file mode 100644 index 0000000..0407e06 --- /dev/null +++ b/src/pcache.c @@ -0,0 +1,922 @@ +/* +** 2008 August 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 that page cache. +*/ +#include "sqliteInt.h" + +/* +** A complete page cache is an instance of this structure. Every +** entry in the cache holds a single page of the database file. The +** btree layer only operates on the cached copy of the database pages. +** +** A page cache entry is "clean" if it exactly matches what is currently +** on disk. A page is "dirty" if it has been modified and needs to be +** persisted to disk. +** +** pDirty, pDirtyTail, pSynced: +** All dirty pages are linked into the doubly linked list using +** PgHdr.pDirtyNext and pDirtyPrev. The list is maintained in LRU order +** such that p was added to the list more recently than p->pDirtyNext. +** PCache.pDirty points to the first (newest) element in the list and +** pDirtyTail to the last (oldest). +** +** The PCache.pSynced variable is used to optimize searching for a dirty +** page to eject from the cache mid-transaction. It is better to eject +** a page that does not require a journal sync than one that does. +** Therefore, pSynced is maintained so that it *almost* always points +** to either the oldest page in the pDirty/pDirtyTail list that has a +** clear PGHDR_NEED_SYNC flag or to a page that is older than this one +** (so that the right page to eject can be found by following pDirtyPrev +** pointers). +*/ +struct PCache { + PgHdr *pDirty, *pDirtyTail; /* List of dirty pages in LRU order */ + PgHdr *pSynced; /* Last synced page in dirty page list */ + int nRefSum; /* Sum of ref counts over all pages */ + int szCache; /* Configured cache size */ + int szSpill; /* Size before spilling occurs */ + int szPage; /* Size of every page in this cache */ + int szExtra; /* Size of extra space for each page */ + u8 bPurgeable; /* True if pages are on backing store */ + u8 eCreate; /* eCreate value for for xFetch() */ + int (*xStress)(void*,PgHdr*); /* Call to try make a page clean */ + void *pStress; /* Argument to xStress */ + sqlite3_pcache *pCache; /* Pluggable cache module */ +}; + +/********************************** Test and Debug Logic **********************/ +/* +** Debug tracing macros. Enable by by changing the "0" to "1" and +** recompiling. +** +** When sqlite3PcacheTrace is 1, single line trace messages are issued. +** When sqlite3PcacheTrace is 2, a dump of the pcache showing all cache entries +** is displayed for many operations, resulting in a lot of output. +*/ +#if defined(SQLITE_DEBUG) && 0 + int sqlite3PcacheTrace = 2; /* 0: off 1: simple 2: cache dumps */ + int sqlite3PcacheMxDump = 9999; /* Max cache entries for pcacheDump() */ +# define pcacheTrace(X) if(sqlite3PcacheTrace){sqlite3DebugPrintf X;} + static void pcachePageTrace(int i, sqlite3_pcache_page *pLower){ + PgHdr *pPg; + unsigned char *a; + int j; + pPg = (PgHdr*)pLower->pExtra; + printf("%3d: nRef %2d flgs %02x data ", i, pPg->nRef, pPg->flags); + a = (unsigned char *)pLower->pBuf; + for(j=0; j<12; j++) printf("%02x", a[j]); + printf(" ptr %p\n", pPg); + } + static void pcacheDump(PCache *pCache){ + int N; + int i; + sqlite3_pcache_page *pLower; + + if( sqlite3PcacheTrace<2 ) return; + if( pCache->pCache==0 ) return; + N = sqlite3PcachePagecount(pCache); + if( N>sqlite3PcacheMxDump ) N = sqlite3PcacheMxDump; + for(i=1; i<=N; i++){ + pLower = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, i, 0); + if( pLower==0 ) continue; + pcachePageTrace(i, pLower); + if( ((PgHdr*)pLower)->pPage==0 ){ + sqlite3GlobalConfig.pcache2.xUnpin(pCache->pCache, pLower, 0); + } + } + } +#else +# define pcacheTrace(X) +# define pcachePageTrace(PGNO, X) +# define pcacheDump(X) +#endif + +/* +** Return 1 if pPg is on the dirty list for pCache. Return 0 if not. +** This routine runs inside of assert() statements only. +*/ +#ifdef SQLITE_DEBUG +static int pageOnDirtyList(PCache *pCache, PgHdr *pPg){ + PgHdr *p; + for(p=pCache->pDirty; p; p=p->pDirtyNext){ + if( p==pPg ) return 1; + } + return 0; +} +#endif + +/* +** Check invariants on a PgHdr entry. Return true if everything is OK. +** Return false if any invariant is violated. +** +** This routine is for use inside of assert() statements only. For +** example: +** +** assert( sqlite3PcachePageSanity(pPg) ); +*/ +#ifdef SQLITE_DEBUG +int sqlite3PcachePageSanity(PgHdr *pPg){ + PCache *pCache; + assert( pPg!=0 ); + assert( pPg->pgno>0 || pPg->pPager==0 ); /* Page number is 1 or more */ + pCache = pPg->pCache; + assert( pCache!=0 ); /* Every page has an associated PCache */ + if( pPg->flags & PGHDR_CLEAN ){ + assert( (pPg->flags & PGHDR_DIRTY)==0 );/* Cannot be both CLEAN and DIRTY */ + assert( !pageOnDirtyList(pCache, pPg) );/* CLEAN pages not on dirty list */ + }else{ + assert( (pPg->flags & PGHDR_DIRTY)!=0 );/* If not CLEAN must be DIRTY */ + assert( pPg->pDirtyNext==0 || pPg->pDirtyNext->pDirtyPrev==pPg ); + assert( pPg->pDirtyPrev==0 || pPg->pDirtyPrev->pDirtyNext==pPg ); + assert( pPg->pDirtyPrev!=0 || pCache->pDirty==pPg ); + assert( pageOnDirtyList(pCache, pPg) ); + } + /* WRITEABLE pages must also be DIRTY */ + if( pPg->flags & PGHDR_WRITEABLE ){ + assert( pPg->flags & PGHDR_DIRTY ); /* WRITEABLE implies DIRTY */ + } + /* NEED_SYNC can be set independently of WRITEABLE. This can happen, + ** for example, when using the sqlite3PagerDontWrite() optimization: + ** (1) Page X is journalled, and gets WRITEABLE and NEED_SEEK. + ** (2) Page X moved to freelist, WRITEABLE is cleared + ** (3) Page X reused, WRITEABLE is set again + ** If NEED_SYNC had been cleared in step 2, then it would not be reset + ** in step 3, and page might be written into the database without first + ** syncing the rollback journal, which might cause corruption on a power + ** loss. + ** + ** Another example is when the database page size is smaller than the + ** disk sector size. When any page of a sector is journalled, all pages + ** in that sector are marked NEED_SYNC even if they are still CLEAN, just + ** in case they are later modified, since all pages in the same sector + ** must be journalled and synced before any of those pages can be safely + ** written. + */ + return 1; +} +#endif /* SQLITE_DEBUG */ + + +/********************************** Linked List Management ********************/ + +/* Allowed values for second argument to pcacheManageDirtyList() */ +#define PCACHE_DIRTYLIST_REMOVE 1 /* Remove pPage from dirty list */ +#define PCACHE_DIRTYLIST_ADD 2 /* Add pPage to the dirty list */ +#define PCACHE_DIRTYLIST_FRONT 3 /* Move pPage to the front of the list */ + +/* +** Manage pPage's participation on the dirty list. Bits of the addRemove +** argument determines what operation to do. The 0x01 bit means first +** remove pPage from the dirty list. The 0x02 means add pPage back to +** the dirty list. Doing both moves pPage to the front of the dirty list. +*/ +static void pcacheManageDirtyList(PgHdr *pPage, u8 addRemove){ + PCache *p = pPage->pCache; + + pcacheTrace(("%p.DIRTYLIST.%s %d\n", p, + addRemove==1 ? "REMOVE" : addRemove==2 ? "ADD" : "FRONT", + pPage->pgno)); + if( addRemove & PCACHE_DIRTYLIST_REMOVE ){ + assert( pPage->pDirtyNext || pPage==p->pDirtyTail ); + assert( pPage->pDirtyPrev || pPage==p->pDirty ); + + /* Update the PCache1.pSynced variable if necessary. */ + if( p->pSynced==pPage ){ + p->pSynced = pPage->pDirtyPrev; + } + + if( pPage->pDirtyNext ){ + pPage->pDirtyNext->pDirtyPrev = pPage->pDirtyPrev; + }else{ + assert( pPage==p->pDirtyTail ); + p->pDirtyTail = pPage->pDirtyPrev; + } + if( pPage->pDirtyPrev ){ + pPage->pDirtyPrev->pDirtyNext = pPage->pDirtyNext; + }else{ + /* If there are now no dirty pages in the cache, set eCreate to 2. + ** This is an optimization that allows sqlite3PcacheFetch() to skip + ** searching for a dirty page to eject from the cache when it might + ** otherwise have to. */ + assert( pPage==p->pDirty ); + p->pDirty = pPage->pDirtyNext; + assert( p->bPurgeable || p->eCreate==2 ); + if( p->pDirty==0 ){ /*OPTIMIZATION-IF-TRUE*/ + assert( p->bPurgeable==0 || p->eCreate==1 ); + p->eCreate = 2; + } + } + } + if( addRemove & PCACHE_DIRTYLIST_ADD ){ + pPage->pDirtyPrev = 0; + pPage->pDirtyNext = p->pDirty; + if( pPage->pDirtyNext ){ + assert( pPage->pDirtyNext->pDirtyPrev==0 ); + pPage->pDirtyNext->pDirtyPrev = pPage; + }else{ + p->pDirtyTail = pPage; + if( p->bPurgeable ){ + assert( p->eCreate==2 ); + p->eCreate = 1; + } + } + p->pDirty = pPage; + + /* If pSynced is NULL and this page has a clear NEED_SYNC flag, set + ** pSynced to point to it. Checking the NEED_SYNC flag is an + ** optimization, as if pSynced points to a page with the NEED_SYNC + ** flag set sqlite3PcacheFetchStress() searches through all newer + ** entries of the dirty-list for a page with NEED_SYNC clear anyway. */ + if( !p->pSynced + && 0==(pPage->flags&PGHDR_NEED_SYNC) /*OPTIMIZATION-IF-FALSE*/ + ){ + p->pSynced = pPage; + } + } + pcacheDump(p); +} + +/* +** Wrapper around the pluggable caches xUnpin method. If the cache is +** being used for an in-memory database, this function is a no-op. +*/ +static void pcacheUnpin(PgHdr *p){ + if( p->pCache->bPurgeable ){ + pcacheTrace(("%p.UNPIN %d\n", p->pCache, p->pgno)); + sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 0); + pcacheDump(p->pCache); + } +} + +/* +** Compute the number of pages of cache requested. p->szCache is the +** cache size requested by the "PRAGMA cache_size" statement. +*/ +static int numberOfCachePages(PCache *p){ + if( p->szCache>=0 ){ + /* IMPLEMENTATION-OF: R-42059-47211 If the argument N is positive then the + ** suggested cache size is set to N. */ + return p->szCache; + }else{ + i64 n; + /* IMPLEMANTATION-OF: R-59858-46238 If the argument N is negative, then the + ** number of cache pages is adjusted to be a number of pages that would + ** use approximately abs(N*1024) bytes of memory based on the current + ** page size. */ + n = ((-1024*(i64)p->szCache)/(p->szPage+p->szExtra)); + if( n>1000000000 ) n = 1000000000; + return (int)n; + } +} + +/*************************************************** General Interfaces ****** +** +** Initialize and shutdown the page cache subsystem. Neither of these +** functions are threadsafe. +*/ +int sqlite3PcacheInitialize(void){ + if( sqlite3GlobalConfig.pcache2.xInit==0 ){ + /* IMPLEMENTATION-OF: R-26801-64137 If the xInit() method is NULL, then the + ** built-in default page cache is used instead of the application defined + ** page cache. */ + sqlite3PCacheSetDefault(); + assert( sqlite3GlobalConfig.pcache2.xInit!=0 ); + } + return sqlite3GlobalConfig.pcache2.xInit(sqlite3GlobalConfig.pcache2.pArg); +} +void sqlite3PcacheShutdown(void){ + if( sqlite3GlobalConfig.pcache2.xShutdown ){ + /* IMPLEMENTATION-OF: R-26000-56589 The xShutdown() method may be NULL. */ + sqlite3GlobalConfig.pcache2.xShutdown(sqlite3GlobalConfig.pcache2.pArg); + } +} + +/* +** Return the size in bytes of a PCache object. +*/ +int sqlite3PcacheSize(void){ return sizeof(PCache); } + +/* +** Create a new PCache object. Storage space to hold the object +** has already been allocated and is passed in as the p pointer. +** The caller discovers how much space needs to be allocated by +** calling sqlite3PcacheSize(). +** +** szExtra is some extra space allocated for each page. The first +** 8 bytes of the extra space will be zeroed as the page is allocated, +** but remaining content will be uninitialized. Though it is opaque +** to this module, the extra space really ends up being the MemPage +** structure in the pager. +*/ +int sqlite3PcacheOpen( + int szPage, /* Size of every page */ + int szExtra, /* Extra space associated with each page */ + int bPurgeable, /* True if pages are on backing store */ + int (*xStress)(void*,PgHdr*),/* Call to try to make pages clean */ + void *pStress, /* Argument to xStress */ + PCache *p /* Preallocated space for the PCache */ +){ + memset(p, 0, sizeof(PCache)); + p->szPage = 1; + p->szExtra = szExtra; + assert( szExtra>=8 ); /* First 8 bytes will be zeroed */ + p->bPurgeable = bPurgeable; + p->eCreate = 2; + p->xStress = xStress; + p->pStress = pStress; + p->szCache = 100; + p->szSpill = 1; + pcacheTrace(("%p.OPEN szPage %d bPurgeable %d\n",p,szPage,bPurgeable)); + return sqlite3PcacheSetPageSize(p, szPage); +} + +/* +** Change the page size for PCache object. The caller must ensure that there +** are no outstanding page references when this function is called. +*/ +int sqlite3PcacheSetPageSize(PCache *pCache, int szPage){ + assert( pCache->nRefSum==0 && pCache->pDirty==0 ); + if( pCache->szPage ){ + sqlite3_pcache *pNew; + pNew = sqlite3GlobalConfig.pcache2.xCreate( + szPage, pCache->szExtra + ROUND8(sizeof(PgHdr)), + pCache->bPurgeable + ); + if( pNew==0 ) return SQLITE_NOMEM_BKPT; + sqlite3GlobalConfig.pcache2.xCachesize(pNew, numberOfCachePages(pCache)); + if( pCache->pCache ){ + sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache); + } + pCache->pCache = pNew; + pCache->szPage = szPage; + pcacheTrace(("%p.PAGESIZE %d\n",pCache,szPage)); + } + return SQLITE_OK; +} + +/* +** Try to obtain a page from the cache. +** +** This routine returns a pointer to an sqlite3_pcache_page object if +** such an object is already in cache, or if a new one is created. +** This routine returns a NULL pointer if the object was not in cache +** and could not be created. +** +** The createFlags should be 0 to check for existing pages and should +** be 3 (not 1, but 3) to try to create a new page. +** +** If the createFlag is 0, then NULL is always returned if the page +** is not already in the cache. If createFlag is 1, then a new page +** is created only if that can be done without spilling dirty pages +** and without exceeding the cache size limit. +** +** The caller needs to invoke sqlite3PcacheFetchFinish() to properly +** initialize the sqlite3_pcache_page object and convert it into a +** PgHdr object. The sqlite3PcacheFetch() and sqlite3PcacheFetchFinish() +** routines are split this way for performance reasons. When separated +** they can both (usually) operate without having to push values to +** the stack on entry and pop them back off on exit, which saves a +** lot of pushing and popping. +*/ +sqlite3_pcache_page *sqlite3PcacheFetch( + PCache *pCache, /* Obtain the page from this cache */ + Pgno pgno, /* Page number to obtain */ + int createFlag /* If true, create page if it does not exist already */ +){ + int eCreate; + sqlite3_pcache_page *pRes; + + assert( pCache!=0 ); + assert( pCache->pCache!=0 ); + assert( createFlag==3 || createFlag==0 ); + assert( pCache->eCreate==((pCache->bPurgeable && pCache->pDirty) ? 1 : 2) ); + + /* eCreate defines what to do if the page does not exist. + ** 0 Do not allocate a new page. (createFlag==0) + ** 1 Allocate a new page if doing so is inexpensive. + ** (createFlag==1 AND bPurgeable AND pDirty) + ** 2 Allocate a new page even it doing so is difficult. + ** (createFlag==1 AND !(bPurgeable AND pDirty) + */ + eCreate = createFlag & pCache->eCreate; + assert( eCreate==0 || eCreate==1 || eCreate==2 ); + assert( createFlag==0 || pCache->eCreate==eCreate ); + assert( createFlag==0 || eCreate==1+(!pCache->bPurgeable||!pCache->pDirty) ); + pRes = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, eCreate); + pcacheTrace(("%p.FETCH %d%s (result: %p) ",pCache,pgno, + createFlag?" create":"",pRes)); + pcachePageTrace(pgno, pRes); + return pRes; +} + +/* +** If the sqlite3PcacheFetch() routine is unable to allocate a new +** page because no clean pages are available for reuse and the cache +** size limit has been reached, then this routine can be invoked to +** try harder to allocate a page. This routine might invoke the stress +** callback to spill dirty pages to the journal. It will then try to +** allocate the new page and will only fail to allocate a new page on +** an OOM error. +** +** This routine should be invoked only after sqlite3PcacheFetch() fails. +*/ +int sqlite3PcacheFetchStress( + PCache *pCache, /* Obtain the page from this cache */ + Pgno pgno, /* Page number to obtain */ + sqlite3_pcache_page **ppPage /* Write result here */ +){ + PgHdr *pPg; + if( pCache->eCreate==2 ) return 0; + + if( sqlite3PcachePagecount(pCache)>pCache->szSpill ){ + /* Find a dirty page to write-out and recycle. First try to find a + ** page that does not require a journal-sync (one with PGHDR_NEED_SYNC + ** cleared), but if that is not possible settle for any other + ** unreferenced dirty page. + ** + ** If the LRU page in the dirty list that has a clear PGHDR_NEED_SYNC + ** flag is currently referenced, then the following may leave pSynced + ** set incorrectly (pointing to other than the LRU page with NEED_SYNC + ** cleared). This is Ok, as pSynced is just an optimization. */ + for(pPg=pCache->pSynced; + pPg && (pPg->nRef || (pPg->flags&PGHDR_NEED_SYNC)); + pPg=pPg->pDirtyPrev + ); + pCache->pSynced = pPg; + if( !pPg ){ + for(pPg=pCache->pDirtyTail; pPg && pPg->nRef; pPg=pPg->pDirtyPrev); + } + if( pPg ){ + int rc; +#ifdef SQLITE_LOG_CACHE_SPILL + sqlite3_log(SQLITE_FULL, + "spill page %d making room for %d - cache used: %d/%d", + pPg->pgno, pgno, + sqlite3GlobalConfig.pcache2.xPagecount(pCache->pCache), + numberOfCachePages(pCache)); +#endif + pcacheTrace(("%p.SPILL %d\n",pCache,pPg->pgno)); + rc = pCache->xStress(pCache->pStress, pPg); + pcacheDump(pCache); + if( rc!=SQLITE_OK && rc!=SQLITE_BUSY ){ + return rc; + } + } + } + *ppPage = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, 2); + return *ppPage==0 ? SQLITE_NOMEM_BKPT : SQLITE_OK; +} + +/* +** This is a helper routine for sqlite3PcacheFetchFinish() +** +** In the uncommon case where the page being fetched has not been +** initialized, this routine is invoked to do the initialization. +** This routine is broken out into a separate function since it +** requires extra stack manipulation that can be avoided in the common +** case. +*/ +static SQLITE_NOINLINE PgHdr *pcacheFetchFinishWithInit( + PCache *pCache, /* Obtain the page from this cache */ + Pgno pgno, /* Page number obtained */ + sqlite3_pcache_page *pPage /* Page obtained by prior PcacheFetch() call */ +){ + PgHdr *pPgHdr; + assert( pPage!=0 ); + pPgHdr = (PgHdr*)pPage->pExtra; + assert( pPgHdr->pPage==0 ); + memset(&pPgHdr->pDirty, 0, sizeof(PgHdr) - offsetof(PgHdr,pDirty)); + pPgHdr->pPage = pPage; + pPgHdr->pData = pPage->pBuf; + pPgHdr->pExtra = (void *)&pPgHdr[1]; + memset(pPgHdr->pExtra, 0, 8); + pPgHdr->pCache = pCache; + pPgHdr->pgno = pgno; + pPgHdr->flags = PGHDR_CLEAN; + return sqlite3PcacheFetchFinish(pCache,pgno,pPage); +} + +/* +** This routine converts the sqlite3_pcache_page object returned by +** sqlite3PcacheFetch() into an initialized PgHdr object. This routine +** must be called after sqlite3PcacheFetch() in order to get a usable +** result. +*/ +PgHdr *sqlite3PcacheFetchFinish( + PCache *pCache, /* Obtain the page from this cache */ + Pgno pgno, /* Page number obtained */ + sqlite3_pcache_page *pPage /* Page obtained by prior PcacheFetch() call */ +){ + PgHdr *pPgHdr; + + assert( pPage!=0 ); + pPgHdr = (PgHdr *)pPage->pExtra; + + if( !pPgHdr->pPage ){ + return pcacheFetchFinishWithInit(pCache, pgno, pPage); + } + pCache->nRefSum++; + pPgHdr->nRef++; + assert( sqlite3PcachePageSanity(pPgHdr) ); + return pPgHdr; +} + +/* +** Decrement the reference count on a page. If the page is clean and the +** reference count drops to 0, then it is made eligible for recycling. +*/ +void SQLITE_NOINLINE sqlite3PcacheRelease(PgHdr *p){ + assert( p->nRef>0 ); + p->pCache->nRefSum--; + if( (--p->nRef)==0 ){ + if( p->flags&PGHDR_CLEAN ){ + pcacheUnpin(p); + }else{ + pcacheManageDirtyList(p, PCACHE_DIRTYLIST_FRONT); + assert( sqlite3PcachePageSanity(p) ); + } + } +} + +/* +** Increase the reference count of a supplied page by 1. +*/ +void sqlite3PcacheRef(PgHdr *p){ + assert(p->nRef>0); + assert( sqlite3PcachePageSanity(p) ); + p->nRef++; + p->pCache->nRefSum++; +} + +/* +** Drop a page from the cache. There must be exactly one reference to the +** page. This function deletes that reference, so after it returns the +** page pointed to by p is invalid. +*/ +void sqlite3PcacheDrop(PgHdr *p){ + assert( p->nRef==1 ); + assert( sqlite3PcachePageSanity(p) ); + if( p->flags&PGHDR_DIRTY ){ + pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE); + } + p->pCache->nRefSum--; + sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 1); +} + +/* +** Make sure the page is marked as dirty. If it isn't dirty already, +** make it so. +*/ +void sqlite3PcacheMakeDirty(PgHdr *p){ + assert( p->nRef>0 ); + assert( sqlite3PcachePageSanity(p) ); + if( p->flags & (PGHDR_CLEAN|PGHDR_DONT_WRITE) ){ /*OPTIMIZATION-IF-FALSE*/ + p->flags &= ~PGHDR_DONT_WRITE; + if( p->flags & PGHDR_CLEAN ){ + p->flags ^= (PGHDR_DIRTY|PGHDR_CLEAN); + pcacheTrace(("%p.DIRTY %d\n",p->pCache,p->pgno)); + assert( (p->flags & (PGHDR_DIRTY|PGHDR_CLEAN))==PGHDR_DIRTY ); + pcacheManageDirtyList(p, PCACHE_DIRTYLIST_ADD); + assert( sqlite3PcachePageSanity(p) ); + } + assert( sqlite3PcachePageSanity(p) ); + } +} + +/* +** Make sure the page is marked as clean. If it isn't clean already, +** make it so. +*/ +void sqlite3PcacheMakeClean(PgHdr *p){ + assert( sqlite3PcachePageSanity(p) ); + assert( (p->flags & PGHDR_DIRTY)!=0 ); + assert( (p->flags & PGHDR_CLEAN)==0 ); + pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE); + p->flags &= ~(PGHDR_DIRTY|PGHDR_NEED_SYNC|PGHDR_WRITEABLE); + p->flags |= PGHDR_CLEAN; + pcacheTrace(("%p.CLEAN %d\n",p->pCache,p->pgno)); + assert( sqlite3PcachePageSanity(p) ); + if( p->nRef==0 ){ + pcacheUnpin(p); + } +} + +/* +** Make every page in the cache clean. +*/ +void sqlite3PcacheCleanAll(PCache *pCache){ + PgHdr *p; + pcacheTrace(("%p.CLEAN-ALL\n",pCache)); + while( (p = pCache->pDirty)!=0 ){ + sqlite3PcacheMakeClean(p); + } +} + +/* +** Clear the PGHDR_NEED_SYNC and PGHDR_WRITEABLE flag from all dirty pages. +*/ +void sqlite3PcacheClearWritable(PCache *pCache){ + PgHdr *p; + pcacheTrace(("%p.CLEAR-WRITEABLE\n",pCache)); + for(p=pCache->pDirty; p; p=p->pDirtyNext){ + p->flags &= ~(PGHDR_NEED_SYNC|PGHDR_WRITEABLE); + } + pCache->pSynced = pCache->pDirtyTail; +} + +/* +** Clear the PGHDR_NEED_SYNC flag from all dirty pages. +*/ +void sqlite3PcacheClearSyncFlags(PCache *pCache){ + PgHdr *p; + for(p=pCache->pDirty; p; p=p->pDirtyNext){ + p->flags &= ~PGHDR_NEED_SYNC; + } + pCache->pSynced = pCache->pDirtyTail; +} + +/* +** Change the page number of page p to newPgno. +*/ +void sqlite3PcacheMove(PgHdr *p, Pgno newPgno){ + PCache *pCache = p->pCache; + sqlite3_pcache_page *pOther; + assert( p->nRef>0 ); + assert( newPgno>0 ); + assert( sqlite3PcachePageSanity(p) ); + pcacheTrace(("%p.MOVE %d -> %d\n",pCache,p->pgno,newPgno)); + pOther = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, newPgno, 0); + if( pOther ){ + PgHdr *pXPage = (PgHdr*)pOther->pExtra; + assert( pXPage->nRef==0 ); + pXPage->nRef++; + pCache->nRefSum++; + sqlite3PcacheDrop(pXPage); + } + sqlite3GlobalConfig.pcache2.xRekey(pCache->pCache, p->pPage, p->pgno,newPgno); + p->pgno = newPgno; + if( (p->flags&PGHDR_DIRTY) && (p->flags&PGHDR_NEED_SYNC) ){ + pcacheManageDirtyList(p, PCACHE_DIRTYLIST_FRONT); + assert( sqlite3PcachePageSanity(p) ); + } +} + +/* +** Drop every cache entry whose page number is greater than "pgno". The +** caller must ensure that there are no outstanding references to any pages +** other than page 1 with a page number greater than pgno. +** +** If there is a reference to page 1 and the pgno parameter passed to this +** function is 0, then the data area associated with page 1 is zeroed, but +** the page object is not dropped. +*/ +void sqlite3PcacheTruncate(PCache *pCache, Pgno pgno){ + if( pCache->pCache ){ + PgHdr *p; + PgHdr *pNext; + pcacheTrace(("%p.TRUNCATE %d\n",pCache,pgno)); + for(p=pCache->pDirty; p; p=pNext){ + pNext = p->pDirtyNext; + /* This routine never gets call with a positive pgno except right + ** after sqlite3PcacheCleanAll(). So if there are dirty pages, + ** it must be that pgno==0. + */ + assert( p->pgno>0 ); + if( p->pgno>pgno ){ + assert( p->flags&PGHDR_DIRTY ); + sqlite3PcacheMakeClean(p); + } + } + if( pgno==0 && pCache->nRefSum ){ + sqlite3_pcache_page *pPage1; + pPage1 = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache,1,0); + if( ALWAYS(pPage1) ){ /* Page 1 is always available in cache, because + ** pCache->nRefSum>0 */ + memset(pPage1->pBuf, 0, pCache->szPage); + pgno = 1; + } + } + sqlite3GlobalConfig.pcache2.xTruncate(pCache->pCache, pgno+1); + } +} + +/* +** Close a cache. +*/ +void sqlite3PcacheClose(PCache *pCache){ + assert( pCache->pCache!=0 ); + pcacheTrace(("%p.CLOSE\n",pCache)); + sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache); +} + +/* +** Discard the contents of the cache. +*/ +void sqlite3PcacheClear(PCache *pCache){ + sqlite3PcacheTruncate(pCache, 0); +} + +/* +** Merge two lists of pages connected by pDirty and in pgno order. +** Do not bother fixing the pDirtyPrev pointers. +*/ +static PgHdr *pcacheMergeDirtyList(PgHdr *pA, PgHdr *pB){ + PgHdr result, *pTail; + pTail = &result; + assert( pA!=0 && pB!=0 ); + for(;;){ + if( pA->pgno<pB->pgno ){ + pTail->pDirty = pA; + pTail = pA; + pA = pA->pDirty; + if( pA==0 ){ + pTail->pDirty = pB; + break; + } + }else{ + pTail->pDirty = pB; + pTail = pB; + pB = pB->pDirty; + if( pB==0 ){ + pTail->pDirty = pA; + break; + } + } + } + return result.pDirty; +} + +/* +** Sort the list of pages in accending order by pgno. Pages are +** connected by pDirty pointers. The pDirtyPrev pointers are +** corrupted by this sort. +** +** Since there cannot be more than 2^31 distinct pages in a database, +** there cannot be more than 31 buckets required by the merge sorter. +** One extra bucket is added to catch overflow in case something +** ever changes to make the previous sentence incorrect. +*/ +#define N_SORT_BUCKET 32 +static PgHdr *pcacheSortDirtyList(PgHdr *pIn){ + PgHdr *a[N_SORT_BUCKET], *p; + int i; + memset(a, 0, sizeof(a)); + while( pIn ){ + p = pIn; + pIn = p->pDirty; + p->pDirty = 0; + for(i=0; ALWAYS(i<N_SORT_BUCKET-1); i++){ + if( a[i]==0 ){ + a[i] = p; + break; + }else{ + p = pcacheMergeDirtyList(a[i], p); + a[i] = 0; + } + } + if( NEVER(i==N_SORT_BUCKET-1) ){ + /* To get here, there need to be 2^(N_SORT_BUCKET) elements in + ** the input list. But that is impossible. + */ + a[i] = pcacheMergeDirtyList(a[i], p); + } + } + p = a[0]; + for(i=1; i<N_SORT_BUCKET; i++){ + if( a[i]==0 ) continue; + p = p ? pcacheMergeDirtyList(p, a[i]) : a[i]; + } + return p; +} + +/* +** Return a list of all dirty pages in the cache, sorted by page number. +*/ +PgHdr *sqlite3PcacheDirtyList(PCache *pCache){ + PgHdr *p; + for(p=pCache->pDirty; p; p=p->pDirtyNext){ + p->pDirty = p->pDirtyNext; + } + return pcacheSortDirtyList(pCache->pDirty); +} + +/* +** Return the total number of references to all pages held by the cache. +** +** This is not the total number of pages referenced, but the sum of the +** reference count for all pages. +*/ +int sqlite3PcacheRefCount(PCache *pCache){ + return pCache->nRefSum; +} + +/* +** Return the number of references to the page supplied as an argument. +*/ +int sqlite3PcachePageRefcount(PgHdr *p){ + return p->nRef; +} + +/* +** Return the total number of pages in the cache. +*/ +int sqlite3PcachePagecount(PCache *pCache){ + assert( pCache->pCache!=0 ); + return sqlite3GlobalConfig.pcache2.xPagecount(pCache->pCache); +} + +#ifdef SQLITE_TEST +/* +** Get the suggested cache-size value. +*/ +int sqlite3PcacheGetCachesize(PCache *pCache){ + return numberOfCachePages(pCache); +} +#endif + +/* +** Set the suggested cache-size value. +*/ +void sqlite3PcacheSetCachesize(PCache *pCache, int mxPage){ + assert( pCache->pCache!=0 ); + pCache->szCache = mxPage; + sqlite3GlobalConfig.pcache2.xCachesize(pCache->pCache, + numberOfCachePages(pCache)); +} + +/* +** Set the suggested cache-spill value. Make no changes if if the +** argument is zero. Return the effective cache-spill size, which will +** be the larger of the szSpill and szCache. +*/ +int sqlite3PcacheSetSpillsize(PCache *p, int mxPage){ + int res; + assert( p->pCache!=0 ); + if( mxPage ){ + if( mxPage<0 ){ + mxPage = (int)((-1024*(i64)mxPage)/(p->szPage+p->szExtra)); + } + p->szSpill = mxPage; + } + res = numberOfCachePages(p); + if( res<p->szSpill ) res = p->szSpill; + return res; +} + +/* +** Free up as much memory as possible from the page cache. +*/ +void sqlite3PcacheShrink(PCache *pCache){ + assert( pCache->pCache!=0 ); + sqlite3GlobalConfig.pcache2.xShrink(pCache->pCache); +} + +/* +** Return the size of the header added by this middleware layer +** in the page-cache hierarchy. +*/ +int sqlite3HeaderSizePcache(void){ return ROUND8(sizeof(PgHdr)); } + +/* +** Return the number of dirty pages currently in the cache, as a percentage +** of the configured cache size. +*/ +int sqlite3PCachePercentDirty(PCache *pCache){ + PgHdr *pDirty; + int nDirty = 0; + int nCache = numberOfCachePages(pCache); + for(pDirty=pCache->pDirty; pDirty; pDirty=pDirty->pDirtyNext) nDirty++; + return nCache ? (int)(((i64)nDirty * 100) / nCache) : 0; +} + +#ifdef SQLITE_DIRECT_OVERFLOW_READ +/* +** Return true if there are one or more dirty pages in the cache. Else false. +*/ +int sqlite3PCacheIsDirty(PCache *pCache){ + return (pCache->pDirty!=0); +} +#endif + +#if defined(SQLITE_CHECK_PAGES) || defined(SQLITE_DEBUG) +/* +** For all dirty pages currently in the cache, invoke the specified +** callback. This is only used if the SQLITE_CHECK_PAGES macro is +** defined. +*/ +void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *)){ + PgHdr *pDirty; + for(pDirty=pCache->pDirty; pDirty; pDirty=pDirty->pDirtyNext){ + xIter(pDirty); + } +} +#endif |