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Memory-mapped I/O is now on by default. The "PRAGMA mmap_limit(N)" can be

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used to issue a hint to the VFS to limit mmap space to N bytes.  The VFS
is free to ignore that hint if desired.  However, if "PRAGMA mmap_limit(0)"
is used, xFetch is never called.

FossilOrigin-Name: 1b37c4effdd03aa2ea938a71b4f22ed27391689b
This commit is contained in:
drh
2013-03-25 23:09:28 +00:00
parent d1ab8065c1
commit 0d0614bdc6
18 changed files with 84 additions and 92 deletions
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15
src/os_unix.c
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@@ -225,6 +225,11 @@ struct unixFile {
const char *zPath; /* Name of the file */
unixShm *pShm; /* Shared memory segment information */
int szChunk; /* Configured by FCNTL_CHUNK_SIZE */
int nFetchOut; /* Number of outstanding xFetch refs */
sqlite3_int64 mmapSize; /* Usable size of mapping at pMapRegion */
sqlite3_int64 mmapOrigsize; /* Actual size of mapping at pMapRegion */
sqlite3_int64 mmapLimit; /* Configured FCNTL_MMAP_LIMIT value */
void *pMapRegion; /* Memory mapped region */
#ifdef __QNXNTO__
int sectorSize; /* Device sector size */
int deviceCharacteristics; /* Precomputed device characteristics */
@@ -251,11 +256,6 @@ struct unixFile {
unsigned char inNormalWrite; /* True if in a normal write operation */
#endif
sqlite3_int64 mmapSize; /* Usable size of mapping at pMapRegion */
sqlite3_int64 mmapOrigsize; /* Actual size of mapping at pMapRegion */
sqlite3_int64 mmapLimit; /* Configured FCNTL_MMAP_SIZE value */
void *pMapRegion; /* Memory mapped region */
int nFetchOut; /* Number of outstanding xFetch refs */
#ifdef SQLITE_TEST
/* In test mode, increase the size of this structure a bit so that
@@ -3699,7 +3699,7 @@ static int unixFileControl(sqlite3_file *id, int op, void *pArg){
}
return SQLITE_OK;
}
case SQLITE_FCNTL_MMAP_SIZE: {
case SQLITE_FCNTL_MMAP_LIMIT: {
pFile->mmapLimit = *(i64*)pArg;
return SQLITE_OK;
}
@@ -4528,7 +4528,7 @@ static void unixUnmapfile(unixFile *pFd){
** the mapping to create. Otherwise, if nByte is less than zero, then the
** requested size is the size of the file on disk. The actual size of the
** created mapping is either the requested size or the value configured
** using SQLITE_FCNTL_MMAP_SIZE, whichever is smaller.
** using SQLITE_FCNTL_MMAP_LIMIT, whichever is smaller.
**
** SQLITE_OK is returned if no error occurs (even if the mapping is not
** recreated as a result of outstanding references) or an SQLite error
@@ -4969,6 +4969,7 @@ static int fillInUnixFile(
pNew->pVfs = pVfs;
pNew->zPath = zFilename;
pNew->ctrlFlags = (u8)ctrlFlags;
pNew->mmapLimit = SQLITE_DEFAULT_MMAP_LIMIT;
if( sqlite3_uri_boolean(((ctrlFlags & UNIXFILE_URI) ? zFilename : 0),
"psow", SQLITE_POWERSAFE_OVERWRITE) ){
pNew->ctrlFlags |= UNIXFILE_PSOW;