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Overview
Comment:Expand scope of the SQLITE_MAX_MMAP_SIZE define for the Win32 VFS.
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SHA1:f4b8faab45e217f227bd7ce65d4741754731b8cd
User & Date: mistachkin 2013-04-15 20:08:27
Context
2013-04-16
14:52
Disable memory-mapped I/O when the codec is enabled. check-in: 340cca30 user: drh tags: trunk
2013-04-15
20:08
Expand scope of the SQLITE_MAX_MMAP_SIZE define for the Win32 VFS. check-in: f4b8faab user: mistachkin tags: trunk
17:03
Refactoring the mmap interface. The controlling pragma is now "mmap_size" instead of "mmap_limit". Also change SQLITE_CONFIG_MMAP_LIMIT and SQLITE_FCNTL_MMAP_LIMIT to SQLITE_CONFIG_MMAP_SIZE and SQLITE_FCNTL_MMAP_SIZE, respecctively. The default mmap_size is now always 0, meaning that memory mapped I/O is off by default. There is a new compile-time option SQLITE_MAX_MMAP_SIZE that determines a hard upper bound on the mmap_size. Setting SQLITE_MAX_MMAP_SIZE to zero disables the memory-mapped I/O logic and causes it to be omitted from the build. An extra argument is added to SQLITE_CONFIG_MMAP_SIZE that can optionally lower the SQLITE_MAX_MMAP_SIZE at start-time. The SQLITE_MAX_MMAP_SIZE is zero for platforms where we know that it does not work, meaning that it cannot be turned on by mistake on those platforms. check-in: ea1404a1 user: drh tags: trunk
Changes
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Changes to src/os_win.c.

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#if SQLITE_OS_WINCE
  LPWSTR zDeleteOnClose;  /* Name of file to delete when closing */
  HANDLE hMutex;          /* Mutex used to control access to shared lock */  
  HANDLE hShared;         /* Shared memory segment used for locking */
  winceLock local;        /* Locks obtained by this instance of winFile */
  winceLock *shared;      /* Global shared lock memory for the file  */
#endif

  int nFetchOut;                /* Number of outstanding xFetch references */
  HANDLE hMap;                  /* Handle for accessing memory mapping */
  void *pMapRegion;             /* Area memory mapped */
  sqlite3_int64 mmapSize;       /* Usable size of mapped region */
  sqlite3_int64 mmapSizeActual; /* Actual size of mapped region */
  sqlite3_int64 mmapSizeMax;    /* Configured FCNTL_MMAP_SIZE value */

};

/*
** Allowed values for winFile.ctrlFlags
*/
#define WINFILE_RDONLY          0x02   /* Connection is read only */
#define WINFILE_PERSIST_WAL     0x04   /* Persistent WAL mode */
................................................................................
    return 1;
  }

  return 0;
#endif
}


/* Forward references to VFS methods */
static int winUnmapfile(winFile*);


/*
** Close a file.
**
** It is reported that an attempt to close a handle might sometimes
** fail.  This is a very unreasonable result, but Windows is notorious
** for being unreasonable so I do not doubt that it might happen.  If
................................................................................
  assert( id!=0 );
#ifndef SQLITE_OMIT_WAL
  assert( pFile->pShm==0 );
#endif
  OSTRACE(("CLOSE %d\n", pFile->h));
  assert( pFile->h!=NULL && pFile->h!=INVALID_HANDLE_VALUE );


  rc = winUnmapfile(pFile);
  if( rc!=SQLITE_OK ) return rc;


  do{
    rc = osCloseHandle(pFile->h);
    /* SimulateIOError( rc=0; cnt=MX_CLOSE_ATTEMPT; ); */
  }while( rc==0 && ++cnt < MX_CLOSE_ATTEMPT && (sqlite3_win32_sleep(100), 1) );
#if SQLITE_OS_WINCE
#define WINCE_DELETION_ATTEMPTS 3
................................................................................
      char *zTFile = sqlite3MallocZero( pFile->pVfs->mxPathname );
      if( zTFile ){
        getTempname(pFile->pVfs->mxPathname, zTFile);
        *(char**)pArg = zTFile;
      }
      return SQLITE_OK;
    }

    case SQLITE_FCNTL_MMAP_SIZE: {
      i64 newLimit = *(i64*)pArg;
      if( newLimit>sqlite3GlobalConfig.mxMmap ){
        newLimit = sqlite3GlobalConfig.mxMmap;
      }
      *(i64*)pArg = pFile->mmapSizeMax;
      if( newLimit>=0 ) pFile->mmapSizeMax = newLimit;
      return SQLITE_OK;
    }

  }
  return SQLITE_NOTFOUND;
}

/*
** Return the sector size in bytes of the underlying block device for
** the specified file. This is almost always 512 bytes, but may be
................................................................................
# define winShmBarrier 0
# define winShmUnmap   0
#endif /* #ifndef SQLITE_OMIT_WAL */

/*
** Cleans up the mapped region of the specified file, if any.
*/

static int winUnmapfile(winFile *pFile){
  assert( pFile!=0 );
#if SQLITE_MAX_MMAP_SIZE>0
  if( pFile->pMapRegion ){
    if( !osUnmapViewOfFile(pFile->pMapRegion) ){
      pFile->lastErrno = osGetLastError();
      return winLogError(SQLITE_IOERR_MMAP, pFile->lastErrno,
                         "winUnmap1", pFile->zPath);
    }
    pFile->pMapRegion = 0;
................................................................................
    if( !osCloseHandle(pFile->hMap) ){
      pFile->lastErrno = osGetLastError();
      return winLogError(SQLITE_IOERR_MMAP, pFile->lastErrno,
                         "winUnmap2", pFile->zPath);
    }
    pFile->hMap = NULL;
  }
#endif
  return SQLITE_OK;
}

#if SQLITE_MAX_MMAP_SIZE>0
/*
** Memory map or remap the file opened by file-descriptor pFd (if the file
** is already mapped, the existing mapping is replaced by the new). Or, if 
** there already exists a mapping for this file, and there are still 
** outstanding xFetch() references to it, this function is a no-op.
**
** If parameter nByte is non-negative, then it is the requested size of 
................................................................................
** Finally, if an error does occur, return an SQLite error code. The final
** value of *pp is undefined in this case.
**
** If this function does return a pointer, the caller must eventually 
** release the reference by calling unixUnfetch().
*/
static int winFetch(sqlite3_file *fd, i64 iOff, int nAmt, void **pp){

  winFile *pFd = (winFile*)fd;   /* The underlying database file */

  *pp = 0;

#if SQLITE_MAX_MMAP_SIZE>0
  if( pFd->mmapSizeMax>0 ){
    if( pFd->pMapRegion==0 ){
      int rc = winMapfile(pFd, -1);
      if( rc!=SQLITE_OK ) return rc;
................................................................................
** argument that was passed to the unixFetch() invocation. 
**
** Or, if the third argument is NULL, then this function is being called 
** to inform the VFS layer that, according to POSIX, any existing mapping 
** may now be invalid and should be unmapped.
*/
static int winUnfetch(sqlite3_file *fd, i64 iOff, void *p){

  winFile *pFd = (winFile*)fd;   /* The underlying database file */

  /* If p==0 (unmap the entire file) then there must be no outstanding 
  ** xFetch references. Or, if p!=0 (meaning it is an xFetch reference),
  ** then there must be at least one outstanding.  */
  assert( (p==0)==(pFd->nFetchOut==0) );

................................................................................
    ** file while a mapping is held, then the following winUnmapfile() call
    ** is unnecessary can can be omitted - potentially improving
    ** performance.  */
    winUnmapfile(pFd);
  }

  assert( pFd->nFetchOut>=0 );

  return SQLITE_OK;
}

/*
** Here ends the implementation of all sqlite3_file methods.
**
********************** End sqlite3_file Methods *******************************
................................................................................
    pFile->ctrlFlags |= WINFILE_RDONLY;
  }
  if( sqlite3_uri_boolean(zName, "psow", SQLITE_POWERSAFE_OVERWRITE) ){
    pFile->ctrlFlags |= WINFILE_PSOW;
  }
  pFile->lastErrno = NO_ERROR;
  pFile->zPath = zName;

  pFile->hMap = NULL;
  pFile->pMapRegion = 0;
  pFile->mmapSize = 0;
  pFile->mmapSizeActual = 0;
  pFile->mmapSizeMax = sqlite3GlobalConfig.mxMmap;


  OpenCounter(+1);
  return rc;
}

/*
** Delete the named file.







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#if SQLITE_OS_WINCE
  LPWSTR zDeleteOnClose;  /* Name of file to delete when closing */
  HANDLE hMutex;          /* Mutex used to control access to shared lock */  
  HANDLE hShared;         /* Shared memory segment used for locking */
  winceLock local;        /* Locks obtained by this instance of winFile */
  winceLock *shared;      /* Global shared lock memory for the file  */
#endif
#if SQLITE_MAX_MMAP_SIZE>0
  int nFetchOut;                /* Number of outstanding xFetch references */
  HANDLE hMap;                  /* Handle for accessing memory mapping */
  void *pMapRegion;             /* Area memory mapped */
  sqlite3_int64 mmapSize;       /* Usable size of mapped region */
  sqlite3_int64 mmapSizeActual; /* Actual size of mapped region */
  sqlite3_int64 mmapSizeMax;    /* Configured FCNTL_MMAP_SIZE value */
#endif
};

/*
** Allowed values for winFile.ctrlFlags
*/
#define WINFILE_RDONLY          0x02   /* Connection is read only */
#define WINFILE_PERSIST_WAL     0x04   /* Persistent WAL mode */
................................................................................
    return 1;
  }

  return 0;
#endif
}

#if SQLITE_MAX_MMAP_SIZE>0
/* Forward references to VFS methods */
static int winUnmapfile(winFile*);
#endif

/*
** Close a file.
**
** It is reported that an attempt to close a handle might sometimes
** fail.  This is a very unreasonable result, but Windows is notorious
** for being unreasonable so I do not doubt that it might happen.  If
................................................................................
  assert( id!=0 );
#ifndef SQLITE_OMIT_WAL
  assert( pFile->pShm==0 );
#endif
  OSTRACE(("CLOSE %d\n", pFile->h));
  assert( pFile->h!=NULL && pFile->h!=INVALID_HANDLE_VALUE );

#if SQLITE_MAX_MMAP_SIZE>0
  rc = winUnmapfile(pFile);
  if( rc!=SQLITE_OK ) return rc;
#endif

  do{
    rc = osCloseHandle(pFile->h);
    /* SimulateIOError( rc=0; cnt=MX_CLOSE_ATTEMPT; ); */
  }while( rc==0 && ++cnt < MX_CLOSE_ATTEMPT && (sqlite3_win32_sleep(100), 1) );
#if SQLITE_OS_WINCE
#define WINCE_DELETION_ATTEMPTS 3
................................................................................
      char *zTFile = sqlite3MallocZero( pFile->pVfs->mxPathname );
      if( zTFile ){
        getTempname(pFile->pVfs->mxPathname, zTFile);
        *(char**)pArg = zTFile;
      }
      return SQLITE_OK;
    }
#if SQLITE_MAX_MMAP_SIZE>0
    case SQLITE_FCNTL_MMAP_SIZE: {
      i64 newLimit = *(i64*)pArg;
      if( newLimit>sqlite3GlobalConfig.mxMmap ){
        newLimit = sqlite3GlobalConfig.mxMmap;
      }
      *(i64*)pArg = pFile->mmapSizeMax;
      if( newLimit>=0 ) pFile->mmapSizeMax = newLimit;
      return SQLITE_OK;
    }
#endif
  }
  return SQLITE_NOTFOUND;
}

/*
** Return the sector size in bytes of the underlying block device for
** the specified file. This is almost always 512 bytes, but may be
................................................................................
# define winShmBarrier 0
# define winShmUnmap   0
#endif /* #ifndef SQLITE_OMIT_WAL */

/*
** Cleans up the mapped region of the specified file, if any.
*/
#if SQLITE_MAX_MMAP_SIZE>0
static int winUnmapfile(winFile *pFile){
  assert( pFile!=0 );

  if( pFile->pMapRegion ){
    if( !osUnmapViewOfFile(pFile->pMapRegion) ){
      pFile->lastErrno = osGetLastError();
      return winLogError(SQLITE_IOERR_MMAP, pFile->lastErrno,
                         "winUnmap1", pFile->zPath);
    }
    pFile->pMapRegion = 0;
................................................................................
    if( !osCloseHandle(pFile->hMap) ){
      pFile->lastErrno = osGetLastError();
      return winLogError(SQLITE_IOERR_MMAP, pFile->lastErrno,
                         "winUnmap2", pFile->zPath);
    }
    pFile->hMap = NULL;
  }

  return SQLITE_OK;
}


/*
** Memory map or remap the file opened by file-descriptor pFd (if the file
** is already mapped, the existing mapping is replaced by the new). Or, if 
** there already exists a mapping for this file, and there are still 
** outstanding xFetch() references to it, this function is a no-op.
**
** If parameter nByte is non-negative, then it is the requested size of 
................................................................................
** Finally, if an error does occur, return an SQLite error code. The final
** value of *pp is undefined in this case.
**
** If this function does return a pointer, the caller must eventually 
** release the reference by calling unixUnfetch().
*/
static int winFetch(sqlite3_file *fd, i64 iOff, int nAmt, void **pp){
#if SQLITE_MAX_MMAP_SIZE>0
  winFile *pFd = (winFile*)fd;   /* The underlying database file */
#endif
  *pp = 0;

#if SQLITE_MAX_MMAP_SIZE>0
  if( pFd->mmapSizeMax>0 ){
    if( pFd->pMapRegion==0 ){
      int rc = winMapfile(pFd, -1);
      if( rc!=SQLITE_OK ) return rc;
................................................................................
** argument that was passed to the unixFetch() invocation. 
**
** Or, if the third argument is NULL, then this function is being called 
** to inform the VFS layer that, according to POSIX, any existing mapping 
** may now be invalid and should be unmapped.
*/
static int winUnfetch(sqlite3_file *fd, i64 iOff, void *p){
#if SQLITE_MAX_MMAP_SIZE>0
  winFile *pFd = (winFile*)fd;   /* The underlying database file */

  /* If p==0 (unmap the entire file) then there must be no outstanding 
  ** xFetch references. Or, if p!=0 (meaning it is an xFetch reference),
  ** then there must be at least one outstanding.  */
  assert( (p==0)==(pFd->nFetchOut==0) );

................................................................................
    ** file while a mapping is held, then the following winUnmapfile() call
    ** is unnecessary can can be omitted - potentially improving
    ** performance.  */
    winUnmapfile(pFd);
  }

  assert( pFd->nFetchOut>=0 );
#endif
  return SQLITE_OK;
}

/*
** Here ends the implementation of all sqlite3_file methods.
**
********************** End sqlite3_file Methods *******************************
................................................................................
    pFile->ctrlFlags |= WINFILE_RDONLY;
  }
  if( sqlite3_uri_boolean(zName, "psow", SQLITE_POWERSAFE_OVERWRITE) ){
    pFile->ctrlFlags |= WINFILE_PSOW;
  }
  pFile->lastErrno = NO_ERROR;
  pFile->zPath = zName;
#if SQLITE_MAX_MMAP_SIZE>0
  pFile->hMap = NULL;
  pFile->pMapRegion = 0;
  pFile->mmapSize = 0;
  pFile->mmapSizeActual = 0;
  pFile->mmapSizeMax = sqlite3GlobalConfig.mxMmap;
#endif

  OpenCounter(+1);
  return rc;
}

/*
** Delete the named file.