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Overview
Comment: | Provide an alternative and experimental pcache implementation that avoids the use of mutexes at the expense of using more memory. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | mutex-free-pcache |
Files: | files | file ages | folders |
SHA1: |
2ea5bd12872275894715cd9d5b30ef7e |
User & Date: | drh 2011-01-14 16:12:19.274 |
Original Comment: | Provide an alternative and experimental pcache implementation that avoids the use of mutexes at the expense of using more memory. |
Context
2011-01-14
| ||
16:12 | Provide an alternative and experimental pcache implementation that avoids the use of mutexes at the expense of using more memory. (Closed-Leaf check-in: 2ea5bd1287 user: drh tags: mutex-free-pcache) | |
15:17 | Fix comments, including some documentation comments, in the page cache logic. No code changes. (check-in: c80e9c1a0d user: drh tags: trunk) | |
Changes
Changes to Makefile.in.
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169 170 171 172 173 174 175 | fts3_snippet.lo fts3_tokenizer.lo fts3_tokenizer1.lo fts3_write.lo \ func.lo global.lo hash.lo \ icu.lo insert.lo journal.lo legacy.lo loadext.lo \ main.lo malloc.lo mem0.lo mem1.lo mem2.lo mem3.lo mem5.lo \ memjournal.lo \ mutex.lo mutex_noop.lo mutex_os2.lo mutex_unix.lo mutex_w32.lo \ notify.lo opcodes.lo os.lo os_os2.lo os_unix.lo os_win.lo \ | | > | 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 | fts3_snippet.lo fts3_tokenizer.lo fts3_tokenizer1.lo fts3_write.lo \ func.lo global.lo hash.lo \ icu.lo insert.lo journal.lo legacy.lo loadext.lo \ main.lo malloc.lo mem0.lo mem1.lo mem2.lo mem3.lo mem5.lo \ memjournal.lo \ mutex.lo mutex_noop.lo mutex_os2.lo mutex_unix.lo mutex_w32.lo \ notify.lo opcodes.lo os.lo os_os2.lo os_unix.lo os_win.lo \ pager.lo parse.lo pcache.lo pcache1.lo pcache2.lo \ pragma.lo prepare.lo printf.lo \ random.lo resolve.lo rowset.lo rtree.lo select.lo status.lo \ table.lo tokenize.lo trigger.lo \ update.lo util.lo vacuum.lo \ vdbe.lo vdbeapi.lo vdbeaux.lo vdbeblob.lo vdbemem.lo vdbetrace.lo \ wal.lo walker.lo where.lo utf.lo vtab.lo # Object files for the amalgamation. |
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243 244 245 246 247 248 249 250 251 252 253 254 255 256 | $(TOP)/src/os_win.c \ $(TOP)/src/pager.c \ $(TOP)/src/pager.h \ $(TOP)/src/parse.y \ $(TOP)/src/pcache.c \ $(TOP)/src/pcache.h \ $(TOP)/src/pcache1.c \ $(TOP)/src/pragma.c \ $(TOP)/src/prepare.c \ $(TOP)/src/printf.c \ $(TOP)/src/random.c \ $(TOP)/src/resolve.c \ $(TOP)/src/rowset.c \ $(TOP)/src/select.c \ | > | 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 | $(TOP)/src/os_win.c \ $(TOP)/src/pager.c \ $(TOP)/src/pager.h \ $(TOP)/src/parse.y \ $(TOP)/src/pcache.c \ $(TOP)/src/pcache.h \ $(TOP)/src/pcache1.c \ $(TOP)/src/pcache2.c \ $(TOP)/src/pragma.c \ $(TOP)/src/prepare.c \ $(TOP)/src/printf.c \ $(TOP)/src/random.c \ $(TOP)/src/resolve.c \ $(TOP)/src/rowset.c \ $(TOP)/src/select.c \ |
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398 399 400 401 402 403 404 405 406 407 408 409 410 411 | $(TOP)/src/pager.c \ $(TOP)/src/pragma.c \ $(TOP)/src/prepare.c \ $(TOP)/src/printf.c \ $(TOP)/src/random.c \ $(TOP)/src/pcache.c \ $(TOP)/src/pcache1.c \ $(TOP)/src/select.c \ $(TOP)/src/tokenize.c \ $(TOP)/src/utf.c \ $(TOP)/src/util.c \ $(TOP)/src/vdbeapi.c \ $(TOP)/src/vdbeaux.c \ $(TOP)/src/vdbe.c \ | > | 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 | $(TOP)/src/pager.c \ $(TOP)/src/pragma.c \ $(TOP)/src/prepare.c \ $(TOP)/src/printf.c \ $(TOP)/src/random.c \ $(TOP)/src/pcache.c \ $(TOP)/src/pcache1.c \ $(TOP)/src/pcache2.c \ $(TOP)/src/select.c \ $(TOP)/src/tokenize.c \ $(TOP)/src/utf.c \ $(TOP)/src/util.c \ $(TOP)/src/vdbeapi.c \ $(TOP)/src/vdbeaux.c \ $(TOP)/src/vdbe.c \ |
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652 653 654 655 656 657 658 659 660 661 662 663 664 665 | $(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/pager.c pcache.lo: $(TOP)/src/pcache.c $(HDR) $(TOP)/src/pcache.h $(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/pcache.c pcache1.lo: $(TOP)/src/pcache1.c $(HDR) $(TOP)/src/pcache.h $(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/pcache1.c os.lo: $(TOP)/src/os.c $(HDR) $(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/os.c os_unix.lo: $(TOP)/src/os_unix.c $(HDR) $(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/os_unix.c | > > > | 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 | $(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/pager.c pcache.lo: $(TOP)/src/pcache.c $(HDR) $(TOP)/src/pcache.h $(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/pcache.c pcache1.lo: $(TOP)/src/pcache1.c $(HDR) $(TOP)/src/pcache.h $(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/pcache1.c pcache2.lo: $(TOP)/src/pcache2.c $(HDR) $(TOP)/src/pcache.h $(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/pcache2.c os.lo: $(TOP)/src/os.c $(HDR) $(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/os.c os_unix.lo: $(TOP)/src/os_unix.c $(HDR) $(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/os_unix.c |
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configure became a regular file.
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install-sh became a regular file.
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Changes to main.mk.
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57 58 59 60 61 62 63 | fts3_snippet.o fts3_tokenizer.o fts3_tokenizer1.o fts3_write.o \ func.o global.o hash.o \ icu.o insert.o journal.o legacy.o loadext.o \ main.o malloc.o mem0.o mem1.o mem2.o mem3.o mem5.o \ memjournal.o \ mutex.o mutex_noop.o mutex_os2.o mutex_unix.o mutex_w32.o \ notify.o opcodes.o os.o os_os2.o os_unix.o os_win.o \ | | > | 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 | fts3_snippet.o fts3_tokenizer.o fts3_tokenizer1.o fts3_write.o \ func.o global.o hash.o \ icu.o insert.o journal.o legacy.o loadext.o \ main.o malloc.o mem0.o mem1.o mem2.o mem3.o mem5.o \ memjournal.o \ mutex.o mutex_noop.o mutex_os2.o mutex_unix.o mutex_w32.o \ notify.o opcodes.o os.o os_os2.o os_unix.o os_win.o \ pager.o parse.o pcache.o pcache1.o pcache2.o \ pragma.o prepare.o printf.o \ random.o resolve.o rowset.o rtree.o select.o status.o \ table.o tokenize.o trigger.o \ update.o util.o vacuum.o \ vdbe.o vdbeapi.o vdbeaux.o vdbeblob.o vdbemem.o vdbetrace.o \ wal.o walker.o where.o utf.o vtab.o |
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124 125 126 127 128 129 130 131 132 133 134 135 136 137 | $(TOP)/src/os_win.c \ $(TOP)/src/pager.c \ $(TOP)/src/pager.h \ $(TOP)/src/parse.y \ $(TOP)/src/pcache.c \ $(TOP)/src/pcache.h \ $(TOP)/src/pcache1.c \ $(TOP)/src/pragma.c \ $(TOP)/src/prepare.c \ $(TOP)/src/printf.c \ $(TOP)/src/random.c \ $(TOP)/src/resolve.c \ $(TOP)/src/rowset.c \ $(TOP)/src/select.c \ | > | 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 | $(TOP)/src/os_win.c \ $(TOP)/src/pager.c \ $(TOP)/src/pager.h \ $(TOP)/src/parse.y \ $(TOP)/src/pcache.c \ $(TOP)/src/pcache.h \ $(TOP)/src/pcache1.c \ $(TOP)/src/pcache2.c \ $(TOP)/src/pragma.c \ $(TOP)/src/prepare.c \ $(TOP)/src/printf.c \ $(TOP)/src/random.c \ $(TOP)/src/resolve.c \ $(TOP)/src/rowset.c \ $(TOP)/src/select.c \ |
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278 279 280 281 282 283 284 285 286 287 288 289 290 291 | $(TOP)/src/pager.c \ $(TOP)/src/pragma.c \ $(TOP)/src/prepare.c \ $(TOP)/src/printf.c \ $(TOP)/src/random.c \ $(TOP)/src/pcache.c \ $(TOP)/src/pcache1.c \ $(TOP)/src/select.c \ $(TOP)/src/tokenize.c \ $(TOP)/src/utf.c \ $(TOP)/src/util.c \ $(TOP)/src/vdbeapi.c \ $(TOP)/src/vdbeaux.c \ $(TOP)/src/vdbe.c \ | > | 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 | $(TOP)/src/pager.c \ $(TOP)/src/pragma.c \ $(TOP)/src/prepare.c \ $(TOP)/src/printf.c \ $(TOP)/src/random.c \ $(TOP)/src/pcache.c \ $(TOP)/src/pcache1.c \ $(TOP)/src/pcache2.c \ $(TOP)/src/select.c \ $(TOP)/src/tokenize.c \ $(TOP)/src/utf.c \ $(TOP)/src/util.c \ $(TOP)/src/vdbeapi.c \ $(TOP)/src/vdbeaux.c \ $(TOP)/src/vdbe.c \ |
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Changes to src/pcache1.c.
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12 13 14 15 16 17 18 19 20 21 22 23 24 25 | ** ** 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 overriden, then neither of ** these two features are available. */ #include "sqliteInt.h" typedef struct PCache1 PCache1; typedef struct PgHdr1 PgHdr1; typedef struct PgFreeslot PgFreeslot; | > | 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 | ** ** 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 overriden, then neither of ** these two features are available. */ #ifndef SQLITE_INDEPENDENT_PCACHE #include "sqliteInt.h" typedef struct PCache1 PCache1; typedef struct PgHdr1 PgHdr1; typedef struct PgFreeslot PgFreeslot; |
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841 842 843 844 845 846 847 | } *pnCurrent = pcache1.nCurrentPage; *pnMax = pcache1.nMaxPage; *pnMin = pcache1.nMinPage; *pnRecyclable = nRecyclable; } #endif | > > | 842 843 844 845 846 847 848 849 850 | } *pnCurrent = pcache1.nCurrentPage; *pnMax = pcache1.nMaxPage; *pnMin = pcache1.nMinPage; *pnRecyclable = nRecyclable; } #endif #endif /* defined(SQLITE_INDEPENDENT_PCACHE) */ |
Added src/pcache2.c.
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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 provides page cache implementation (the sqlite3_pcache ** interface) for when each pager has its own private pcache and ** never has to share it with other pagers. ** ** The advantage to this implementation is that it does not require ** a mutex and hence scales better to multiple threads. The disadvantage ** is that it will use more memory. Hence, this implementation is ** suited for multithreaded applications on multicore workstations ** where memory is plentiful and mutexes are expensive. ** ** The SQLITE_CONFIG_PAGECACHE option to sqlite3_config() and the ** sqlite3_release_memory() interface are no-ops when this particular ** page cache implementation is used. */ #ifdef SQLITE_INDEPENDENT_PCACHE #include "sqliteInt.h" typedef struct PCache2 PCache2; typedef struct PgHdr2 PgHdr2; typedef struct PgFreeslot PgFreeslot; /* 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 PCache2 { /* 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 pcache2CacheSize() method. */ int szPage; /* Size of allocated pages in bytes */ int bPurgeable; /* True if cache is purgeable */ unsigned int nMax; /* Configured "cache_size" value */ /* Hash table of all pages. The following variables may only be accessed ** when the accessor is holding the global mutex (see pcache2EnterMutex() ** and pcache2LeaveMutex()). */ 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[] */ PgHdr2 **apHash; /* Hash table for fast lookup by key */ PgHdr2 *pLruHead, *pLruTail; /* LRU list of unpinned pages */ unsigned int iMaxKey; /* Largest key seen since xTruncate() */ }; /* ** Each cache entry is represented by an instance of the following ** structure. A buffer of PgHdr2->pCache->szPage bytes is allocated ** directly before this structure in memory (see the PGHDR2_TO_PAGE() ** macro below). */ struct PgHdr2 { unsigned int iKey; /* Key value (page number) */ PgHdr2 *pNext; /* Next in hash table chain */ PCache2 *pCache; /* Cache that this page belongs to */ PgHdr2 *pLruNext; /* Next in LRU list of unpinned pages */ PgHdr2 *pLruPrev; /* Previous in LRU list of unpinned pages */ }; /* ** When a PgHdr2 structure is allocated, the associated PCache2.szPage ** bytes of data are located directly before it in memory (i.e. the total ** size of the allocation is sizeof(PgHdr2)+PCache2.szPage byte). The ** PGHDR2_TO_PAGE() macro takes a pointer to a PgHdr2 structure as ** an argument and returns a pointer to the associated block of szPage ** bytes. The PAGE_TO_PGHDR2() macro does the opposite: its argument is ** a pointer to a block of szPage bytes of data and the return value is ** a pointer to the associated PgHdr2 structure. ** ** assert( PGHDR2_TO_PAGE(PAGE_TO_PGHDR2(pCache, X))==X ); */ #define PGHDR2_TO_PAGE(p) (void*)(((char*)p) - p->pCache->szPage) #define PAGE_TO_PGHDR2(c, p) (PgHdr2*)(((char*)p) + c->szPage) /******************************************************************************/ /******** 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. */ void sqlite3PCacheBufferSetup(void *pBuf, int sz, int n){ /* Not used with an independent page cache. All memory from malloc() */ } /* ** Allocate a new page object initially associated with cache pCache. */ static PgHdr2 *pcache2AllocPage(PCache2 *pCache){ int nByte = sizeof(PgHdr2) + pCache->szPage; void *pPg = sqlite3Malloc(nByte); return pPg ? PAGE_TO_PGHDR2(pCache, pPg) : 0; } /* ** Free a page object allocated by pcache2AllocPage(). ** ** The pointer is allowed to be NULL, which is prudent. But it turns out ** that the current implementation happens to never call this routine ** with a NULL pointer, so we mark the NULL test with ALWAYS(). */ static void pcache2FreePage(PgHdr2 *p){ sqlite3_free(PGHDR2_TO_PAGE(p)); } /* ** 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 sqlite3Malloc(sz); } /* ** Free an allocated buffer obtained from sqlite3PageMalloc(). */ void sqlite3PageFree(void *p){ sqlite3_free(p); } /******************************************************************************/ /******** General Implementation Functions ************************************/ /* ** This function is used to resize the hash table used by the cache passed ** as the first argument. */ static int pcache2ResizeHash(PCache2 *p){ PgHdr2 **apNew; unsigned int nNew; unsigned int i; nNew = p->nHash*2; if( nNew<256 ){ nNew = 256; } if( p->nHash ){ sqlite3BeginBenignMalloc(); } apNew = (PgHdr2 **)sqlite3_malloc(sizeof(PgHdr2 *)*nNew); if( p->nHash ){ sqlite3EndBenignMalloc(); } if( apNew ){ memset(apNew, 0, sizeof(PgHdr2 *)*nNew); for(i=0; i<p->nHash; i++){ PgHdr2 *pPage; PgHdr2 *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; } return (p->apHash ? SQLITE_OK : SQLITE_NOMEM); } /* ** This function is used internally to remove the page pPage from the ** global LRU list, if is part of it. If pPage is not part of the global ** LRU list, then this function is a no-op. */ static void pcache2PinPage(PgHdr2 *pPage){ PCache2 *pCache = pPage->pCache; if( pPage && (pPage->pLruNext || pPage==pCache->pLruTail) ){ if( pPage->pLruPrev ){ pPage->pLruPrev->pLruNext = pPage->pLruNext; } if( pPage->pLruNext ){ pPage->pLruNext->pLruPrev = pPage->pLruPrev; } if( pCache->pLruHead==pPage ){ pCache->pLruHead = pPage->pLruNext; } if( pCache->pLruTail==pPage ){ pCache->pLruTail = pPage->pLruPrev; } pPage->pLruNext = 0; pPage->pLruPrev = 0; pPage->pCache->nRecyclable--; } } /* ** Remove the page supplied as an argument from the hash table ** (PCache2.apHash structure) that it is currently stored in. */ static void pcache2RemoveFromHash(PgHdr2 *pPage){ unsigned int h; PCache2 *pCache = pPage->pCache; PgHdr2 **pp; h = pPage->iKey % pCache->nHash; for(pp=&pCache->apHash[h]; (*pp)!=pPage; pp=&(*pp)->pNext); *pp = (*pp)->pNext; pCache->nPage--; } /* ** If there are currently more than pcache.nMaxPage pages allocated, try ** to recycle pages to reduce the number allocated to pcache.nMaxPage. */ static void pcache2EnforceMaxPage(PCache2 *pCache){ while( pCache->nPage>pCache->nMax && pCache->pLruTail ){ PgHdr2 *p = pCache->pLruTail; pcache2PinPage(p); pcache2RemoveFromHash(p); pcache2FreePage(p); } } /* ** 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. */ static void pcache2TruncateUnsafe( PCache2 *pCache, unsigned int iLimit ){ TESTONLY(unsigned int nPage = 0;) /* To assert pCache->nPage is correct */ unsigned int h; for(h=0; h<pCache->nHash; h++){ PgHdr2 **pp = &pCache->apHash[h]; PgHdr2 *pPage; while( (pPage = *pp)!=0 ){ if( pPage->iKey>=iLimit ){ pCache->nPage--; *pp = pPage->pNext; pcache2PinPage(pPage); pcache2FreePage(pPage); }else{ pp = &pPage->pNext; TESTONLY( nPage++; ) } } } assert( pCache->nPage==nPage ); } /******************************************************************************/ /******** sqlite3_pcache Methods **********************************************/ /* ** Implementation of the sqlite3_pcache.xInit method. */ static int pcache2Init(void *NotUsed){ UNUSED_PARAMETER(NotUsed); 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 pcache2Shutdown(void *NotUsed){ UNUSED_PARAMETER(NotUsed); } /* ** Implementation of the sqlite3_pcache.xCreate method. ** ** Allocate a new cache. */ static sqlite3_pcache *pcache2Create(int szPage, int bPurgeable){ PCache2 *pCache; pCache = (PCache2 *)sqlite3_malloc(sizeof(PCache2)); if( pCache ){ memset(pCache, 0, sizeof(PCache2)); pCache->szPage = szPage; pCache->bPurgeable = (bPurgeable ? 1 : 0); } return (sqlite3_pcache *)pCache; } /* ** Implementation of the sqlite3_pcache.xCachesize method. ** ** Configure the cache_size limit for a cache. */ static void pcache2Cachesize(sqlite3_pcache *p, int nMax){ PCache2 *pCache = (PCache2 *)p; if( pCache->bPurgeable ){ pCache->nMax = nMax; pcache2EnforceMaxPage(pCache); } } /* ** Implementation of the sqlite3_pcache.xPagecount method. */ static int pcache2Pagecount(sqlite3_pcache *p){ int n; n = ((PCache2 *)p)->nPage; return n; } /* ** 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-purgable 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 ** PCache2.nMax, 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 ** PCache2.nMax ** ** then attempt to recycle a page from the LRU list. ** ** 5. Otherwise, allocate and return a new page buffer. */ static void *pcache2Fetch(sqlite3_pcache *p, unsigned int iKey, int createFlag){ unsigned int nPinned; PCache2 *pCache = (PCache2 *)p; PgHdr2 *pPage = 0; assert( pCache->bPurgeable || createFlag!=1 ); if( createFlag==1 ) sqlite3BeginBenignMalloc(); /* Search the hash table for an existing entry. */ if( pCache->nHash>0 ){ unsigned int h = iKey % pCache->nHash; for(pPage=pCache->apHash[h]; pPage&&pPage->iKey!=iKey; pPage=pPage->pNext); } if( pPage ){ pcache2PinPage(pPage); goto fetch_out; } if( createFlag==0 ){ goto fetch_out; } /* Step 3 of header comment. */ nPinned = pCache->nPage - pCache->nRecyclable; if( createFlag==1 && nPinned>=pCache->nMax ){ goto fetch_out; } if( pCache->nPage>=pCache->nHash && pcache2ResizeHash(pCache) ){ goto fetch_out; } /* Step 4. Try to recycle a page buffer if appropriate. */ if( pCache->bPurgeable && pCache->pLruTail ){ pPage = pCache->pLruTail; pcache2RemoveFromHash(pPage); pcache2PinPage(pPage); } /* Step 5. If a usable page buffer has still not been found, ** attempt to allocate a new one. */ if( !pPage ){ pPage = pcache2AllocPage(pCache); } 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; *(void **)(PGHDR2_TO_PAGE(pPage)) = 0; pCache->apHash[h] = pPage; } fetch_out: if( pPage && iKey>pCache->iMaxKey ){ pCache->iMaxKey = iKey; } if( createFlag==1 ) sqlite3EndBenignMalloc(); return (pPage ? PGHDR2_TO_PAGE(pPage) : 0); } /* ** Implementation of the sqlite3_pcache.xUnpin method. ** ** Mark a page as unpinned (eligible for asynchronous recycling). */ static void pcache2Unpin(sqlite3_pcache *p, void *pPg, int reuseUnlikely){ PCache2 *pCache = (PCache2 *)p; PgHdr2 *pPage = PAGE_TO_PGHDR2(pCache, pPg); assert( pPage->pCache==pCache ); /* It is an error to call this function if the page is already ** unpinned. */ assert( pPage->pLruPrev==0 && pPage->pLruNext==0 ); assert( pCache->pLruHead!=pPage && pCache->pLruTail!=pPage ); if( reuseUnlikely || pCache->nPage>pCache->nMax ){ pcache2RemoveFromHash(pPage); pcache2FreePage(pPage); }else{ /* Add the page to the LRU list. */ if( pCache->pLruHead ){ pCache->pLruHead->pLruPrev = pPage; pPage->pLruNext = pCache->pLruHead; pCache->pLruHead = pPage; assert( pPage->pLruPrev==0 ); }else{ pCache->pLruTail = pPage; pCache->pLruHead = pPage; assert( pPage->pLruPrev==0 ); assert( pPage->pLruNext==0 ); } pCache->nRecyclable++; } } /* ** Implementation of the sqlite3_pcache.xRekey method. */ static void pcache2Rekey( sqlite3_pcache *p, void *pPg, unsigned int iOld, unsigned int iNew ){ PCache2 *pCache = (PCache2 *)p; PgHdr2 *pPage = PAGE_TO_PGHDR2(pCache, pPg); PgHdr2 **pp; unsigned int h; assert( pPage->iKey==iOld ); assert( pPage->pCache==pCache ); 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; } } /* ** 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 pcache2Truncate(sqlite3_pcache *p, unsigned int iLimit){ PCache2 *pCache = (PCache2 *)p; if( iLimit<=pCache->iMaxKey ){ pcache2TruncateUnsafe(pCache, iLimit); pCache->iMaxKey = iLimit-1; } } /* ** Implementation of the sqlite3_pcache.xDestroy method. ** ** Destroy a cache allocated using pcache2Create(). */ static void pcache2Destroy(sqlite3_pcache *p){ PCache2 *pCache = (PCache2 *)p; assert( pCache->bPurgeable || pCache->nMax==0 ); pcache2TruncateUnsafe(pCache, 0); pcache2EnforceMaxPage(pCache); 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_methods defaultMethods = { 0, /* pArg */ pcache2Init, /* xInit */ pcache2Shutdown, /* xShutdown */ pcache2Create, /* xCreate */ pcache2Cachesize, /* xCachesize */ pcache2Pagecount, /* xPagecount */ pcache2Fetch, /* xFetch */ pcache2Unpin, /* xUnpin */ pcache2Rekey, /* xRekey */ pcache2Truncate, /* xTruncate */ pcache2Destroy /* xDestroy */ }; sqlite3_config(SQLITE_CONFIG_PCACHE, &defaultMethods); } #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){ return 0; } #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 PCache2.nMin for purgeable caches */ int *pnRecyclable /* OUT: Total number of pages available for recycling */ ){ *pnCurrent = 0; *pnMax = 0; *pnMin = 0; *pnRecyclable = 0; } #endif #endif /* SQLITE_INDEPENDENT_PCACHE */ |
Changes to tool/mksqlite3c.tcl.
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239 240 241 242 243 244 245 246 247 248 249 250 251 252 | os_os2.c os_unix.c os_win.c bitvec.c pcache.c pcache1.c rowset.c pager.c wal.c btmutex.c btree.c backup.c | > | 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 | os_os2.c os_unix.c os_win.c bitvec.c pcache.c pcache1.c pcache2.c rowset.c pager.c wal.c btmutex.c btree.c backup.c |
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