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Overview
| Comment: | Hack to have multiple connections to a single file share a single memory mapping of the databse file. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | shared-mapping-hack |
| Files: | files | file ages | folders |
| SHA3-256: |
ec37ad6d08362f4c9faad9b629c0fa23 |
| User & Date: | dan 2017-09-12 18:03:12 |
References
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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 | |
Context
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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 | |
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2017-09-12
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| 18:11 | Merge the mutex-free PRNG change into this branch. check-in: 8b1fc4b9 user: dan tags: shared-mapping-hack | |
| 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 | |
| 15:05 | Fix an error in [b22cdd67] that can cause a negative infinity to be (rarely) reported as a positive infinity. check-in: 9780b23c user: drh tags: trunk | |
Changes
Changes to src/os_unix.c.
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** * Locking primitives for the proxy uber-locking-method. (MacOSX only) ** * Definitions of sqlite3_vfs objects for all locking methods ** plus implementations of sqlite3_os_init() and sqlite3_os_end(). */ #include "sqliteInt.h" #if SQLITE_OS_UNIX /* This file is used on unix only */ /* ** There are various methods for file locking used for concurrency ** control: ** ** 1. POSIX locking (the default), ** 2. No locking, ** 3. Dot-file locking, ................................................................................ #if SQLITE_ENABLE_LOCKING_STYLE unsigned long long sharedByte; /* for AFP simulated shared lock */ #endif #if OS_VXWORKS sem_t *pSem; /* Named POSIX semaphore */ char aSemName[MAX_PATHNAME+2]; /* Name of that semaphore */ #endif }; /* ** A lists of all unixInodeInfo objects. */ static unixInodeInfo *inodeList = 0; /* All unixInodeInfo objects */ static unsigned int nUnusedFd = 0; /* Total unused file descriptors */ ................................................................................ static void releaseInodeInfo(unixFile *pFile){ unixInodeInfo *pInode = pFile->pInode; assert( unixMutexHeld() ); if( ALWAYS(pInode) ){ pInode->nRef--; if( pInode->nRef==0 ){ assert( pInode->pShmNode==0 ); closePendingFds(pFile); if( pInode->pPrev ){ assert( pInode->pPrev->pNext==pInode ); pInode->pPrev->pNext = pInode->pNext; }else{ assert( inodeList==pInode ); inodeList = pInode->pNext; ................................................................................ return SQLITE_OK; } /* ** Close the file. */ static int nolockClose(sqlite3_file *id) { return closeUnixFile(id); } /******************* End of the no-op lock implementation ********************* ******************************************************************************/ /****************************************************************************** ................................................................................ if( newLimit>0 && sizeof(size_t)<8 ){ newLimit = (newLimit & 0x7FFFFFFF); } *(i64*)pArg = pFile->mmapSizeMax; if( newLimit>=0 && newLimit!=pFile->mmapSizeMax && pFile->nFetchOut==0 ){ pFile->mmapSizeMax = newLimit; if( pFile->mmapSize>0 ){ unixUnmapfile(pFile); rc = unixMapfile(pFile, -1); } } return rc; } ................................................................................ #if SQLITE_MAX_MMAP_SIZE>0 /* ** If it is currently memory mapped, unmap file pFd. */ static void unixUnmapfile(unixFile *pFd){ assert( pFd->nFetchOut==0 ); if( pFd->pMapRegion ){ osMunmap(pFd->pMapRegion, pFd->mmapSizeActual); pFd->pMapRegion = 0; pFd->mmapSize = 0; pFd->mmapSizeActual = 0; } } ................................................................................ return SQLITE_IOERR_FSTAT; } nMap = statbuf.st_size; } if( nMap>pFd->mmapSizeMax ){ nMap = pFd->mmapSizeMax; } assert( nMap>0 || (pFd->mmapSize==0 && pFd->pMapRegion==0) ); if( nMap!=pFd->mmapSize ){ unixRemapfile(pFd, nMap); } return SQLITE_OK; ................................................................................ #endif } if( pLockingStyle == &posixIoMethods #if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE || pLockingStyle == &nfsIoMethods #endif ){ unixEnterMutex(); rc = findInodeInfo(pNew, &pNew->pInode); if( rc!=SQLITE_OK ){ /* If an error occurred in findInodeInfo(), close the file descriptor ** immediately, before releasing the mutex. findInodeInfo() may fail ** in two scenarios: |
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** * Locking primitives for the proxy uber-locking-method. (MacOSX only) ** * Definitions of sqlite3_vfs objects for all locking methods ** plus implementations of sqlite3_os_init() and sqlite3_os_end(). */ #include "sqliteInt.h" #if SQLITE_OS_UNIX /* This file is used on unix only */ #define SQLITE_SHARED_MAPPING 1 /* ** There are various methods for file locking used for concurrency ** control: ** ** 1. POSIX locking (the default), ** 2. No locking, ** 3. Dot-file locking, ................................................................................ #if SQLITE_ENABLE_LOCKING_STYLE unsigned long long sharedByte; /* for AFP simulated shared lock */ #endif #if OS_VXWORKS sem_t *pSem; /* Named POSIX semaphore */ char aSemName[MAX_PATHNAME+2]; /* Name of that semaphore */ #endif #ifdef SQLITE_SHARED_MAPPING sqlite3_int64 nSharedMapping; /* Size of mapped region in bytes */ void *pSharedMapping; /* Memory mapped region */ #endif }; /* ** A lists of all unixInodeInfo objects. */ static unixInodeInfo *inodeList = 0; /* All unixInodeInfo objects */ static unsigned int nUnusedFd = 0; /* Total unused file descriptors */ ................................................................................ static void releaseInodeInfo(unixFile *pFile){ unixInodeInfo *pInode = pFile->pInode; assert( unixMutexHeld() ); if( ALWAYS(pInode) ){ pInode->nRef--; if( pInode->nRef==0 ){ assert( pInode->pShmNode==0 ); #ifdef SQLITE_SHARED_MAPPING if( pInode->pSharedMapping ){ osMunmap(pInode->pSharedMapping, pInode->nSharedMapping); pInode->pSharedMapping = 0; pInode->nSharedMapping = 0; } #endif closePendingFds(pFile); if( pInode->pPrev ){ assert( pInode->pPrev->pNext==pInode ); pInode->pPrev->pNext = pInode->pNext; }else{ assert( inodeList==pInode ); inodeList = pInode->pNext; ................................................................................ return SQLITE_OK; } /* ** Close the file. */ static int nolockClose(sqlite3_file *id) { #ifdef SQLITE_SHARED_MAPPING unixFile *pFd = (unixFile*)id; if( pFd->pInode ){ unixEnterMutex(); releaseInodeInfo(pFd); unixLeaveMutex(); } #endif return closeUnixFile(id); } /******************* End of the no-op lock implementation ********************* ******************************************************************************/ /****************************************************************************** ................................................................................ if( newLimit>0 && sizeof(size_t)<8 ){ newLimit = (newLimit & 0x7FFFFFFF); } *(i64*)pArg = pFile->mmapSizeMax; if( newLimit>=0 && newLimit!=pFile->mmapSizeMax && pFile->nFetchOut==0 ){ pFile->mmapSizeMax = newLimit; #ifdef SQLITE_SHARED_MAPPING if( pFile->pInode==0 ) #endif if( pFile->mmapSize>0 ){ unixUnmapfile(pFile); rc = unixMapfile(pFile, -1); } } return rc; } ................................................................................ #if SQLITE_MAX_MMAP_SIZE>0 /* ** If it is currently memory mapped, unmap file pFd. */ static void unixUnmapfile(unixFile *pFd){ assert( pFd->nFetchOut==0 ); #ifdef SQLITE_SHARED_MAPPING if( pFd->pInode ) return; #endif if( pFd->pMapRegion ){ osMunmap(pFd->pMapRegion, pFd->mmapSizeActual); pFd->pMapRegion = 0; pFd->mmapSize = 0; pFd->mmapSizeActual = 0; } } ................................................................................ return SQLITE_IOERR_FSTAT; } nMap = statbuf.st_size; } if( nMap>pFd->mmapSizeMax ){ nMap = pFd->mmapSizeMax; } #ifdef SQLITE_SHARED_MAPPING if( pFd->pInode ){ unixInodeInfo *pInode = pFd->pInode; if( pFd->pMapRegion ) return SQLITE_OK; unixEnterMutex(); if( pInode->pSharedMapping==0 ){ u8 *pNew = osMmap(0, nMap, PROT_READ, MAP_SHARED, pFd->h, 0); if( pNew==MAP_FAILED ){ unixLogError(SQLITE_OK, "mmap", pFd->zPath); pFd->mmapSizeMax = 0; }else{ pInode->pSharedMapping = pNew; pInode->nSharedMapping = nMap; } } pFd->pMapRegion = pInode->pSharedMapping; pFd->mmapSizeActual = pFd->mmapSize = pInode->nSharedMapping; unixLeaveMutex(); return SQLITE_OK; } #endif assert( nMap>0 || (pFd->mmapSize==0 && pFd->pMapRegion==0) ); if( nMap!=pFd->mmapSize ){ unixRemapfile(pFd, nMap); } return SQLITE_OK; ................................................................................ #endif } if( pLockingStyle == &posixIoMethods #if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE || pLockingStyle == &nfsIoMethods #endif #ifdef SQLITE_SHARED_MAPPING || pLockingStyle == &nolockIoMethods #endif ){ unixEnterMutex(); rc = findInodeInfo(pNew, &pNew->pInode); if( rc!=SQLITE_OK ){ /* If an error occurred in findInodeInfo(), close the file descriptor ** immediately, before releasing the mutex. findInodeInfo() may fail ** in two scenarios: |