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Overview
| Comment: | Cherrypick [ec37ad6d08] into this branch. With this patch, if SQLITE_SHARED_MAPPING is defined at build-time SQLite will use a single memory mapping for multiple connections to the same database file within a single process. |
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| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | begin-concurrent |
| Files: | files | file ages | folders |
| SHA3-256: | c7a5880d6d898299b4c9414b7702cfa4 |
| User & Date: | dan 2017-09-22 11:09:09 |
| Wiki: | begin-concurrent |
Context
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2017-11-06
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| 10:04 | Allow "BEGIN CONCURRENT" transactions to modify the temp schema. check-in: 0fb6d91c user: dan tags: begin-concurrent | |
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2017-09-22
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| 11:09 | Cherrypick [ec37ad6d08] into this branch. With this patch, if SQLITE_SHARED_MAPPING is defined at build-time SQLite will use a single memory mapping for multiple connections to the same database file within a single process. check-in: c7a5880d user: dan tags: begin-concurrent | |
| 10:49 | Merge latest trunk changes into this branch. check-in: 307b802e user: dan tags: begin-concurrent | |
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2017-09-12
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| 18:03 | Hack to have multiple connections to a single file share a single memory mapping of the databse file. check-in: ec37ad6d user: dan tags: shared-mapping-hack | |
Changes
Changes to src/os_unix.c.
1111 1111 #if SQLITE_ENABLE_LOCKING_STYLE 1112 1112 unsigned long long sharedByte; /* for AFP simulated shared lock */ 1113 1113 #endif 1114 1114 #if OS_VXWORKS 1115 1115 sem_t *pSem; /* Named POSIX semaphore */ 1116 1116 char aSemName[MAX_PATHNAME+2]; /* Name of that semaphore */ 1117 1117 #endif 1118 +#ifdef SQLITE_SHARED_MAPPING 1119 + sqlite3_int64 nSharedMapping; /* Size of mapped region in bytes */ 1120 + void *pSharedMapping; /* Memory mapped region */ 1121 +#endif 1118 1122 }; 1119 1123 1120 1124 /* 1121 1125 ** A lists of all unixInodeInfo objects. 1122 1126 */ 1123 1127 static unixInodeInfo *inodeList = 0; /* All unixInodeInfo objects */ 1124 1128 static unsigned int nUnusedFd = 0; /* Total unused file descriptors */ ................................................................................ 1245 1249 static void releaseInodeInfo(unixFile *pFile){ 1246 1250 unixInodeInfo *pInode = pFile->pInode; 1247 1251 assert( unixMutexHeld() ); 1248 1252 if( ALWAYS(pInode) ){ 1249 1253 pInode->nRef--; 1250 1254 if( pInode->nRef==0 ){ 1251 1255 assert( pInode->pShmNode==0 ); 1256 +#ifdef SQLITE_SHARED_MAPPING 1257 + if( pInode->pSharedMapping ){ 1258 + osMunmap(pInode->pSharedMapping, pInode->nSharedMapping); 1259 + pInode->pSharedMapping = 0; 1260 + pInode->nSharedMapping = 0; 1261 + } 1262 +#endif 1252 1263 closePendingFds(pFile); 1253 1264 if( pInode->pPrev ){ 1254 1265 assert( pInode->pPrev->pNext==pInode ); 1255 1266 pInode->pPrev->pNext = pInode->pNext; 1256 1267 }else{ 1257 1268 assert( inodeList==pInode ); 1258 1269 inodeList = pInode->pNext; ................................................................................ 2051 2062 return SQLITE_OK; 2052 2063 } 2053 2064 2054 2065 /* 2055 2066 ** Close the file. 2056 2067 */ 2057 2068 static int nolockClose(sqlite3_file *id) { 2069 +#ifdef SQLITE_SHARED_MAPPING 2070 + unixFile *pFd = (unixFile*)id; 2071 + if( pFd->pInode ){ 2072 + unixEnterMutex(); 2073 + releaseInodeInfo(pFd); 2074 + unixLeaveMutex(); 2075 + } 2076 +#endif 2058 2077 return closeUnixFile(id); 2059 2078 } 2060 2079 2061 2080 /******************* End of the no-op lock implementation ********************* 2062 2081 ******************************************************************************/ 2063 2082 2064 2083 /****************************************************************************** ................................................................................ 3870 3889 if( newLimit>0 && sizeof(size_t)<8 ){ 3871 3890 newLimit = (newLimit & 0x7FFFFFFF); 3872 3891 } 3873 3892 3874 3893 *(i64*)pArg = pFile->mmapSizeMax; 3875 3894 if( newLimit>=0 && newLimit!=pFile->mmapSizeMax && pFile->nFetchOut==0 ){ 3876 3895 pFile->mmapSizeMax = newLimit; 3896 +#ifdef SQLITE_SHARED_MAPPING 3897 + if( pFile->pInode==0 ) 3898 +#endif 3877 3899 if( pFile->mmapSize>0 ){ 3878 3900 unixUnmapfile(pFile); 3879 3901 rc = unixMapfile(pFile, -1); 3880 3902 } 3881 3903 } 3882 3904 return rc; 3883 3905 } ................................................................................ 4770 4792 4771 4793 #if SQLITE_MAX_MMAP_SIZE>0 4772 4794 /* 4773 4795 ** If it is currently memory mapped, unmap file pFd. 4774 4796 */ 4775 4797 static void unixUnmapfile(unixFile *pFd){ 4776 4798 assert( pFd->nFetchOut==0 ); 4799 +#ifdef SQLITE_SHARED_MAPPING 4800 + if( pFd->pInode ) return; 4801 +#endif 4777 4802 if( pFd->pMapRegion ){ 4778 4803 osMunmap(pFd->pMapRegion, pFd->mmapSizeActual); 4779 4804 pFd->pMapRegion = 0; 4780 4805 pFd->mmapSize = 0; 4781 4806 pFd->mmapSizeActual = 0; 4782 4807 } 4783 4808 } ................................................................................ 4900 4925 return SQLITE_IOERR_FSTAT; 4901 4926 } 4902 4927 nMap = statbuf.st_size; 4903 4928 } 4904 4929 if( nMap>pFd->mmapSizeMax ){ 4905 4930 nMap = pFd->mmapSizeMax; 4906 4931 } 4932 + 4933 +#ifdef SQLITE_SHARED_MAPPING 4934 + if( pFd->pInode ){ 4935 + unixInodeInfo *pInode = pFd->pInode; 4936 + if( pFd->pMapRegion ) return SQLITE_OK; 4937 + unixEnterMutex(); 4938 + if( pInode->pSharedMapping==0 ){ 4939 + u8 *pNew = osMmap(0, nMap, PROT_READ, MAP_SHARED, pFd->h, 0); 4940 + if( pNew==MAP_FAILED ){ 4941 + unixLogError(SQLITE_OK, "mmap", pFd->zPath); 4942 + pFd->mmapSizeMax = 0; 4943 + }else{ 4944 + pInode->pSharedMapping = pNew; 4945 + pInode->nSharedMapping = nMap; 4946 + } 4947 + } 4948 + pFd->pMapRegion = pInode->pSharedMapping; 4949 + pFd->mmapSizeActual = pFd->mmapSize = pInode->nSharedMapping; 4950 + unixLeaveMutex(); 4951 + return SQLITE_OK; 4952 + } 4953 +#endif 4907 4954 4908 4955 assert( nMap>0 || (pFd->mmapSize==0 && pFd->pMapRegion==0) ); 4909 4956 if( nMap!=pFd->mmapSize ){ 4910 4957 unixRemapfile(pFd, nMap); 4911 4958 } 4912 4959 4913 4960 return SQLITE_OK; ................................................................................ 5339 5386 #endif 5340 5387 } 5341 5388 5342 5389 if( pLockingStyle == &posixIoMethods 5343 5390 #if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE 5344 5391 || pLockingStyle == &nfsIoMethods 5345 5392 #endif 5393 +#ifdef SQLITE_SHARED_MAPPING 5394 + || pLockingStyle == &nolockIoMethods 5395 +#endif 5346 5396 ){ 5347 5397 unixEnterMutex(); 5348 5398 rc = findInodeInfo(pNew, &pNew->pInode); 5349 5399 if( rc!=SQLITE_OK ){ 5350 5400 /* If an error occurred in findInodeInfo(), close the file descriptor 5351 5401 ** immediately, before releasing the mutex. findInodeInfo() may fail 5352 5402 ** in two scenarios: