Index: src/pcache1.c ================================================================== --- src/pcache1.c +++ src/pcache1.c @@ -84,10 +84,28 @@ 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. Unless SQLITE_PCACHE_SEPARATE_HEADER is defined, a buffer of +** PgHdr1.pCache->szPage bytes is allocated directly before this structure +** in memory. +*/ +struct PgHdr1 { + sqlite3_pcache_page page; /* Base class. Must be first. pBuf & pExtra */ + unsigned int iKey; /* Key value (page number) */ + u8 isPinned; /* Page in use, not on the LRU list */ + u8 isBulkLocal; /* This page from bulk local storage */ + u8 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 LRU list of unpinned pages */ + PgHdr1 *pLruPrev; /* Previous in LRU list of unpinned pages */ +}; /* 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. @@ -113,11 +131,11 @@ 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 nCurrentPage; /* Number of purgeable pages allocated */ - PgHdr1 *pLruHead, *pLruTail; /* LRU list of unpinned pages */ + 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 @@ -151,27 +169,10 @@ 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 */ }; -/* -** Each cache entry is represented by an instance of the following -** structure. Unless SQLITE_PCACHE_SEPARATE_HEADER is defined, a buffer of -** PgHdr1.pCache->szPage bytes is allocated directly before this structure -** in memory. -*/ -struct PgHdr1 { - sqlite3_pcache_page page; - unsigned int iKey; /* Key value (page number) */ - u8 isPinned; /* Page in use, not on the LRU list */ - u8 isBulkLocal; /* This page from bulk local storage */ - PgHdr1 *pNext; /* Next in hash table chain */ - PCache1 *pCache; /* Cache that currently owns this page */ - PgHdr1 *pLruNext; /* Next in LRU list of unpinned pages */ - PgHdr1 *pLruPrev; /* Previous in LRU list of unpinned pages */ -}; - /* ** Free slots in the allocator used to divide up the global page cache ** buffer provided using the SQLITE_CONFIG_PAGECACHE mechanism. */ struct PgFreeslot { @@ -227,10 +228,11 @@ # 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 @@ -287,10 +289,11 @@ for(i=0; iszPage]; pX->page.pBuf = zBulk; pX->page.pExtra = &pX[1]; pX->isBulkLocal = 1; + pX->isAnchor = 0; pX->pNext = pCache->pFree; pCache->pFree = pX; zBulk += pCache->szAlloc; } } @@ -429,10 +432,11 @@ #endif if( pPg==0 ) return 0; p->page.pBuf = pPg; p->page.pExtra = &p[1]; p->isBulkLocal = 0; + p->isAnchor = 0; } if( pCache->bPurgeable ){ pCache->pGroup->nCurrentPage++; } return p; @@ -555,26 +559,20 @@ PCache1 *pCache; assert( pPage!=0 ); assert( pPage->isPinned==0 ); pCache = pPage->pCache; - assert( pPage->pLruNext || pPage==pCache->pGroup->pLruTail ); - assert( pPage->pLruPrev || pPage==pCache->pGroup->pLruHead ); + assert( pPage->pLruNext ); + assert( pPage->pLruPrev ); assert( sqlite3_mutex_held(pCache->pGroup->mutex) ); - if( pPage->pLruPrev ){ - pPage->pLruPrev->pLruNext = pPage->pLruNext; - }else{ - pCache->pGroup->pLruHead = pPage->pLruNext; - } - if( pPage->pLruNext ){ - pPage->pLruNext->pLruPrev = pPage->pLruPrev; - }else{ - pCache->pGroup->pLruTail = pPage->pLruPrev; - } + pPage->pLruPrev->pLruNext = pPage->pLruNext; + pPage->pLruNext->pLruPrev = pPage->pLruPrev; pPage->pLruNext = 0; pPage->pLruPrev = 0; pPage->isPinned = 1; + assert( pPage->isAnchor==0 ); + assert( pCache->pGroup->lru.isAnchor==1 ); pCache->nRecyclable--; return pPage; } @@ -603,13 +601,15 @@ ** 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->nCurrentPage>pGroup->nMaxPage && pGroup->pLruTail ){ - PgHdr1 *p = pGroup->pLruTail; + while( pGroup->nCurrentPage>pGroup->nMaxPage + && (p=pGroup->lru.pLruPrev)->isAnchor==0 + ){ assert( p->pCache->pGroup==pGroup ); assert( p->isPinned==0 ); pcache1PinPage(p); pcache1RemoveFromHash(p, 1); } @@ -739,10 +739,14 @@ pGroup = (PGroup*)&pCache[1]; pGroup->mxPinned = 10; }else{ pGroup = &pcache1.grp; } + 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); @@ -846,15 +850,15 @@ if( pCache->nPage>=pCache->nHash ) pcache1ResizeHash(pCache); assert( pCache->nHash>0 && pCache->apHash ); /* Step 4. Try to recycle a page. */ if( pCache->bPurgeable - && pGroup->pLruTail + && !pGroup->lru.pLruPrev->isAnchor && ((pCache->nPage+1>=pCache->nMax) || pcache1UnderMemoryPressure(pCache)) ){ PCache1 *pOther; - pPage = pGroup->pLruTail; + pPage = pGroup->lru.pLruPrev; assert( pPage->isPinned==0 ); pcache1RemoveFromHash(pPage, 0); pcache1PinPage(pPage); pOther = pPage->pCache; if( pOther->szAlloc != pCache->szAlloc ){ @@ -1039,25 +1043,20 @@ /* It is an error to call this function if the page is already ** part of the PGroup LRU list. */ assert( pPage->pLruPrev==0 && pPage->pLruNext==0 ); - assert( pGroup->pLruHead!=pPage && pGroup->pLruTail!=pPage ); assert( pPage->isPinned==1 ); if( reuseUnlikely || pGroup->nCurrentPage>pGroup->nMaxPage ){ pcache1RemoveFromHash(pPage, 1); }else{ /* Add the page to the PGroup LRU list. */ - if( pGroup->pLruHead ){ - pGroup->pLruHead->pLruPrev = pPage; - pPage->pLruNext = pGroup->pLruHead; - pGroup->pLruHead = pPage; - }else{ - pGroup->pLruTail = pPage; - pGroup->pLruHead = pPage; - } + PgHdr1 **ppFirst = &pGroup->lru.pLruNext; + pPage->pLruPrev = &pGroup->lru; + (pPage->pLruNext = *ppFirst)->pLruPrev = pPage; + *ppFirst = pPage; pCache->nRecyclable++; pPage->isPinned = 0; } pcache1LeaveMutex(pCache->pGroup); @@ -1191,11 +1190,13 @@ assert( sqlite3_mutex_notheld(pcache1.grp.mutex) ); assert( sqlite3_mutex_notheld(pcache1.mutex) ); if( sqlite3GlobalConfig.nPage==0 ){ PgHdr1 *p; pcache1EnterMutex(&pcache1.grp); - while( (nReq<0 || nFreeisAnchor==0 + ){ nFree += pcache1MemSize(p->page.pBuf); #ifdef SQLITE_PCACHE_SEPARATE_HEADER nFree += sqlite3MemSize(p); #endif assert( p->isPinned==0 ); @@ -1219,15 +1220,15 @@ 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.pLruHead; p; p=p->pLruNext){ + for(p=pcache1.grp.lru.pLruNext; !p->isAnchor; p=p->pLruNext){ assert( p->isPinned==0 ); nRecyclable++; } *pnCurrent = pcache1.grp.nCurrentPage; *pnMax = (int)pcache1.grp.nMaxPage; *pnMin = (int)pcache1.grp.nMinPage; *pnRecyclable = nRecyclable; } #endif