diff options
Diffstat (limited to 'lib/libsqlite3/src/pcache1.c')
| -rw-r--r-- | lib/libsqlite3/src/pcache1.c | 1235 |
1 files changed, 0 insertions, 1235 deletions
diff --git a/lib/libsqlite3/src/pcache1.c b/lib/libsqlite3/src/pcache1.c deleted file mode 100644 index ee6ac0b955c..00000000000 --- a/lib/libsqlite3/src/pcache1.c +++ /dev/null @@ -1,1235 +0,0 @@ -/* -** 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. -** -** If SQLITE_PCACHE_SEPARATE_HEADER is defined, then the extension is obtained -** using a separate memory allocation from the database page content. This -** seeks to overcome the "clownshoe" problem (also called "internal -** fragmentation" in academic literature) of allocating a few bytes more -** than a power of two with the memory allocator rounding up to the next -** power of two, and leaving the rounded-up space unused. -** -** 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, 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. 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. -** -** 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 nCurrentPage; /* 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) are set when the cache is created. 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 */ - 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() */ - - /* 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; - 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*pCache->nMax; - } - zBulk = pCache->pBulk = sqlite3Malloc( szBulk ); - sqlite3EndBenignMalloc(); - if( zBulk ){ - int nBulk = sqlite3MallocSize(zBulk)/pCache->szAlloc; - int i; - for(i=0; i<nBulk; i++){ - 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; - pCache->pFree = pX; - zBulk += pCache->szAlloc; - } - } - 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 ); - sqlite3StatusSet(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); - sqlite3StatusSet(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){ - int nFreed = 0; - if( p==0 ) return; - if( p>=pcache1.pStart && p<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 - 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)) ){ - 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(); } -#ifdef SQLITE_PCACHE_SEPARATE_HEADER - pPg = pcache1Alloc(pCache->szPage); - p = sqlite3Malloc(sizeof(PgHdr1) + pCache->szExtra); - if( !pPg || !p ){ - pcache1Free(pPg); - sqlite3_free(p); - pPg = 0; - } -#else - pPg = pcache1Alloc(pCache->szAlloc); - p = (PgHdr1 *)&((u8 *)pPg)[pCache->szPage]; -#endif - if( benignMalloc ){ sqlite3EndBenignMalloc(); } -#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT - pcache1EnterMutex(pCache->pGroup); -#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; -} - -/* -** 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); -#ifdef SQLITE_PCACHE_SEPARATE_HEADER - sqlite3_free(p); -#endif - } - if( pCache->bPurgeable ){ - pCache->pGroup->nCurrentPage--; - } -} - -/* -** 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){ - 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){ - PCache1 *pCache; - - assert( pPage!=0 ); - assert( pPage->isPinned==0 ); - pCache = pPage->pCache; - assert( pPage->pLruNext ); - assert( pPage->pLruPrev ); - assert( sqlite3_mutex_held(pCache->pGroup->mutex) ); - 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; -} - - -/* -** 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->nCurrentPage>pGroup->nMaxPage - && (p=pGroup->lru.pLruPrev)->isAnchor==0 - ){ - assert( p->pCache->pGroup==pGroup ); - assert( p->isPinned==0 ); - 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( unsigned int nPage = 0; ) /* To assert pCache->nPage is correct */ - unsigned int h; - assert( sqlite3_mutex_held(pCache->pGroup->mutex) ); - for(h=0; h<pCache->nHash; h++){ - PgHdr1 **pp = &pCache->apHash[h]; - PgHdr1 *pPage; - while( (pPage = *pp)!=0 ){ - if( pPage->iKey>=iLimit ){ - pCache->nPage--; - *pp = pPage->pNext; - if( !pPage->isPinned ) pcache1PinPage(pPage); - pcache1FreePage(pPage); - }else{ - pp = &pPage->pNext; - TESTONLY( nPage++; ) - } - } - } - assert( pCache->nPage==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 = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_LRU); - pcache1.mutex = sqlite3_mutex_alloc(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; - } - 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); - pcache1EnterMutex(pGroup); - pcache1ResizeHash(pCache); - if( bPurgeable ){ - pCache->nMin = 10; - pGroup->nMinPage += pCache->nMin; - pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage; - } - 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; - if( pCache->bPurgeable ){ - PGroup *pGroup = pCache->pGroup; - pcache1EnterMutex(pGroup); - pGroup->nMaxPage += (nMax - pCache->nMax); - pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage; - pCache->nMax = nMax; - 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; - 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( pPage->isPinned==0 ); - pcache1RemoveFromHash(pPage, 0); - pcache1PinPage(pPage); - pOther = pPage->pCache; - if( pOther->szAlloc != pCache->szAlloc ){ - pcache1FreePage(pPage); - pPage = 0; - }else{ - pGroup->nCurrentPage -= (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->pLruPrev = 0; - pPage->pLruNext = 0; - pPage->isPinned = 1; - *(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( !pPage->isPinned ){ - 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->pLruPrev==0 && pPage->pLruNext==0 ); - assert( pPage->isPinned==1 ); - - if( reuseUnlikely || pGroup->nCurrentPage>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++; - pPage->isPinned = 0; - } - - 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 h; - assert( pPage->iKey==iOld ); - assert( pPage->pCache==pCache ); - - pcache1EnterMutex(pCache->pGroup); - - h = iOld%pCache->nHash; - pp = &pCache->apHash[h]; - while( (*pp)!=pPage ){ - pp = &(*pp)->pNext; - } - *pp = pPage->pNext; - - h = iNew%pCache->nHash; - pPage->iKey = iNew; - pPage->pNext = pCache->apHash[h]; - pCache->apHash[h] = 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); - 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.nPage==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); -#ifdef SQLITE_PCACHE_SEPARATE_HEADER - nFree += sqlite3MemSize(p); -#endif - assert( p->isPinned==0 ); - 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( p->isPinned==0 ); - nRecyclable++; - } - *pnCurrent = pcache1.grp.nCurrentPage; - *pnMax = (int)pcache1.grp.nMaxPage; - *pnMin = (int)pcache1.grp.nMinPage; - *pnRecyclable = nRecyclable; -} -#endif |