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When possible, use memory mapping when appending new pages to a database file.

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FossilOrigin-Name: 14135da3cdbafd699563a29608f32347cda28338
This commit is contained in:
dan
2013-03-20 14:26:59 +00:00
parent eecc398374
commit eb97b29345
8 changed files with 70 additions and 24 deletions
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33
src/os_unix.c
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@@ -4434,6 +4434,7 @@ static int unixShmUnmap(
*/
static int unixMremap(
sqlite3_file *fd, /* Main database file */
int flags, /* Mask of SQLITE_MREMAP_XXX flags */
sqlite3_int64 iOff, /* Offset to start mapping at */
sqlite3_int64 nOld, /* Size of old mapping, or zero */
sqlite3_int64 nNew, /* Size of new mapping, or zero */
@@ -4442,8 +4443,35 @@ static int unixMremap(
unixFile *p = (unixFile *)fd; /* The underlying database file */
int rc = SQLITE_OK; /* Return code */
void *pNew = 0; /* New mapping */
i64 nRnd; /* nNew rounded up to 4096 */
assert( iOff==0 );
nRnd = (nNew+4095) & ~(i64)((1 << 12)-1);
/* If the SQLITE_MREMAP_EXTEND flag is set, then the size of the requested
** mapping (nNew bytes) may be greater than the size of the database file.
** If this is the case, extend the file on disk using ftruncate(). */
assert( nNew>0 || (flags & SQLITE_MREMAP_EXTEND)==0 );
if( flags & SQLITE_MREMAP_EXTEND ){
struct stat statbuf; /* Low-level file information */
rc = osFstat(p->h, &statbuf);
if( rc==SQLITE_OK && nNew>statbuf.st_size ){
rc = robust_ftruncate(p->h, nNew);
}
if( rc!=SQLITE_OK ) return rc;
}
#if defined(_GNU_SOURCE) && defined(__linux__)
if( nRnd && nOld ){
void *pOld = *ppMap;
*ppMap = pNew = mremap(pOld, nOld, nNew, MREMAP_MAYMOVE);
if( pNew==MAP_FAILED ){
*ppMap = 0;
return SQLITE_IOERR_MREMAP;
}
return SQLITE_OK;
}
#endif
if( nOld!=0 ){
void *pOld = *ppMap;
@@ -4453,11 +4481,10 @@ static int unixMremap(
if( nNew>0 ){
int flags = PROT_READ;
if( (p->ctrlFlags & UNIXFILE_RDONLY)==0 ) flags |= PROT_WRITE;
nNew = (nNew+4095) & ~(i64)((1 << 12)-1);
pNew = mmap(0, nNew, flags, MAP_SHARED, p->h, iOff);
pNew = mmap(0, nRnd, flags, MAP_SHARED, p->h, iOff);
if( pNew==MAP_FAILED ){
pNew = 0;
rc = SQLITE_IOERR;
rc = SQLITE_IOERR_MREMAP;
}
}