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Overview
| Comment: | Add an experimental fix to avoid attempting to mmap memory from an offset that is not a multiple of the system page size on systems with page sizes larger than 32KB. |
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| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | shm-mapping-fix |
| Files: | files | file ages | folders |
| SHA1: | 6f3a5c24d254fc6faf607b505bdef4a7 |
| User & Date: | dan 2014-03-20 08:59:47 |
Context
|
2014-03-20
| ||
| 09:42 | Add a test to ensure os_unix.c works with 64KiB OS pages. Closed-Leaf check-in: e3d2be3b user: dan tags: shm-mapping-fix | |
| 08:59 | Add an experimental fix to avoid attempting to mmap memory from an offset that is not a multiple of the system page size on systems with page sizes larger than 32KB. check-in: 6f3a5c24 user: dan tags: shm-mapping-fix | |
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2014-03-19
| ||
| 20:01 | Avoid some unnecessary calls to sqlite3VdbeRecordUnpack() that were being made when merging data from two or more temp files together in vdbesort.c check-in: 707ea170 user: dan tags: trunk | |
Changes
Changes to src/os_unix.c.
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pShmNode->sharedMask, pShmNode->exclMask));
}
#endif
return rc;
}
/*
** Purge the unixShmNodeList list of all entries with unixShmNode.nRef==0.
**
** This is not a VFS shared-memory method; it is a utility function called
** by VFS shared-memory methods.
*/
static void unixShmPurge(unixFile *pFd){
unixShmNode *p = pFd->pInode->pShmNode;
assert( unixMutexHeld() );
if( p && p->nRef==0 ){
int i;
assert( p->pInode==pFd->pInode );
sqlite3_mutex_free(p->mutex);
for(i=0; i<p->nRegion; i++){
if( p->h>=0 ){
osMunmap(p->apRegion[i], p->szRegion);
}else{
sqlite3_free(p->apRegion[i]);
}
}
sqlite3_free(p->apRegion);
................................................................................
int bExtend, /* True to extend file if necessary */
void volatile **pp /* OUT: Mapped memory */
){
unixFile *pDbFd = (unixFile*)fd;
unixShm *p;
unixShmNode *pShmNode;
int rc = SQLITE_OK;
/* If the shared-memory file has not yet been opened, open it now. */
if( pDbFd->pShm==0 ){
rc = unixOpenSharedMemory(pDbFd);
if( rc!=SQLITE_OK ) return rc;
}
................................................................................
pShmNode = p->pShmNode;
sqlite3_mutex_enter(pShmNode->mutex);
assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );
assert( pShmNode->pInode==pDbFd->pInode );
assert( pShmNode->h>=0 || pDbFd->pInode->bProcessLock==1 );
assert( pShmNode->h<0 || pDbFd->pInode->bProcessLock==0 );
if( pShmNode->nRegion<=iRegion ){
char **apNew; /* New apRegion[] array */
int nByte = (iRegion+1)*szRegion; /* Minimum required file size */
struct stat sStat; /* Used by fstat() */
pShmNode->szRegion = szRegion;
if( pShmNode->h>=0 ){
/* The requested region is not mapped into this processes address space.
** Check to see if it has been allocated (i.e. if the wal-index file is
................................................................................
}
}
}
}
/* Map the requested memory region into this processes address space. */
apNew = (char **)sqlite3_realloc(
pShmNode->apRegion, (iRegion+1)*sizeof(char *)
);
if( !apNew ){
rc = SQLITE_IOERR_NOMEM;
goto shmpage_out;
}
pShmNode->apRegion = apNew;
while(pShmNode->nRegion<=iRegion){
void *pMem;
if( pShmNode->h>=0 ){
pMem = osMmap(0, szRegion,
pShmNode->isReadonly ? PROT_READ : PROT_READ|PROT_WRITE,
MAP_SHARED, pShmNode->h, szRegion*(i64)pShmNode->nRegion
);
if( pMem==MAP_FAILED ){
rc = unixLogError(SQLITE_IOERR_SHMMAP, "mmap", pShmNode->zFilename);
goto shmpage_out;
}
................................................................................
pMem = sqlite3_malloc(szRegion);
if( pMem==0 ){
rc = SQLITE_NOMEM;
goto shmpage_out;
}
memset(pMem, 0, szRegion);
}
pShmNode->apRegion[pShmNode->nRegion] = pMem;
pShmNode->nRegion++;
}
}
shmpage_out:
if( pShmNode->nRegion>iRegion ){
*pp = pShmNode->apRegion[iRegion];
}else{
................................................................................
osMunmap(pFd->pMapRegion, pFd->mmapSizeActual);
pFd->pMapRegion = 0;
pFd->mmapSize = 0;
pFd->mmapSizeActual = 0;
}
}
/*
** Return the system page size.
*/
static int unixGetPagesize(void){
#if HAVE_MREMAP
return 512;
#elif defined(_BSD_SOURCE)
return getpagesize();
#else
return (int)sysconf(_SC_PAGESIZE);
#endif
}
/*
** Attempt to set the size of the memory mapping maintained by file
** descriptor pFd to nNew bytes. Any existing mapping is discarded.
**
** If successful, this function sets the following variables:
**
** unixFile.pMapRegion
................................................................................
assert( nNew>0 );
assert( pFd->mmapSizeActual>=pFd->mmapSize );
assert( MAP_FAILED!=0 );
if( (pFd->ctrlFlags & UNIXFILE_RDONLY)==0 ) flags |= PROT_WRITE;
if( pOrig ){
const int szSyspage = unixGetPagesize();
i64 nReuse = (pFd->mmapSize & ~(szSyspage-1));
u8 *pReq = &pOrig[nReuse];
/* Unmap any pages of the existing mapping that cannot be reused. */
if( nReuse!=nOrig ){
osMunmap(pReq, nOrig-nReuse);
}
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pShmNode->sharedMask, pShmNode->exclMask));
}
#endif
return rc;
}
/*
** Return the system page size.
*/
static int unixGetPagesize(void){
#if defined(_BSD_SOURCE)
return getpagesize();
#else
return (int)sysconf(_SC_PAGESIZE);
#endif
}
/*
** Return the minimum number of 32KB shm regions that should be mapped at
** a time, assuming that each mapping must be an integer multiple of the
** current system page-size.
**
** Usually, this is 1. The exception seems to be systems that are configured
** to use 64KB pages - in this case each mapping must cover at least two
** shm regions.
*/
static int unixShmRegionPerMap(void){
int shmsz = 32*1024; /* SHM region size */
int pgsz = unixGetPagesize(); /* System page size */
assert( ((pgsz-1)&pgsz)==0 ); /* Page size must be a power of 2 */
if( pgsz<shmsz ) return 1;
return pgsz/shmsz;
}
/*
** Purge the unixShmNodeList list of all entries with unixShmNode.nRef==0.
**
** This is not a VFS shared-memory method; it is a utility function called
** by VFS shared-memory methods.
*/
static void unixShmPurge(unixFile *pFd){
unixShmNode *p = pFd->pInode->pShmNode;
assert( unixMutexHeld() );
if( p && p->nRef==0 ){
int nShmPerMap = unixShmRegionPerMap();
int i;
assert( p->pInode==pFd->pInode );
sqlite3_mutex_free(p->mutex);
for(i=0; i<p->nRegion; i+=nShmPerMap){
if( p->h>=0 ){
osMunmap(p->apRegion[i], p->szRegion);
}else{
sqlite3_free(p->apRegion[i]);
}
}
sqlite3_free(p->apRegion);
................................................................................
int bExtend, /* True to extend file if necessary */
void volatile **pp /* OUT: Mapped memory */
){
unixFile *pDbFd = (unixFile*)fd;
unixShm *p;
unixShmNode *pShmNode;
int rc = SQLITE_OK;
int nShmPerMap = unixShmRegionPerMap();
int nReqRegion;
/* If the shared-memory file has not yet been opened, open it now. */
if( pDbFd->pShm==0 ){
rc = unixOpenSharedMemory(pDbFd);
if( rc!=SQLITE_OK ) return rc;
}
................................................................................
pShmNode = p->pShmNode;
sqlite3_mutex_enter(pShmNode->mutex);
assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );
assert( pShmNode->pInode==pDbFd->pInode );
assert( pShmNode->h>=0 || pDbFd->pInode->bProcessLock==1 );
assert( pShmNode->h<0 || pDbFd->pInode->bProcessLock==0 );
/* Minimum number of regions required to be mapped. */
nReqRegion = ((iRegion+nShmPerMap) / nShmPerMap) * nShmPerMap;
if( pShmNode->nRegion<nReqRegion ){
char **apNew; /* New apRegion[] array */
int nByte = nReqRegion*szRegion; /* Minimum required file size */
struct stat sStat; /* Used by fstat() */
pShmNode->szRegion = szRegion;
if( pShmNode->h>=0 ){
/* The requested region is not mapped into this processes address space.
** Check to see if it has been allocated (i.e. if the wal-index file is
................................................................................
}
}
}
}
/* Map the requested memory region into this processes address space. */
apNew = (char **)sqlite3_realloc(
pShmNode->apRegion, nReqRegion*sizeof(char *)
);
if( !apNew ){
rc = SQLITE_IOERR_NOMEM;
goto shmpage_out;
}
pShmNode->apRegion = apNew;
while( pShmNode->nRegion<nReqRegion ){
int nMap = szRegion*nShmPerMap;
int i;
void *pMem;
if( pShmNode->h>=0 ){
pMem = osMmap(0, nMap,
pShmNode->isReadonly ? PROT_READ : PROT_READ|PROT_WRITE,
MAP_SHARED, pShmNode->h, szRegion*(i64)pShmNode->nRegion
);
if( pMem==MAP_FAILED ){
rc = unixLogError(SQLITE_IOERR_SHMMAP, "mmap", pShmNode->zFilename);
goto shmpage_out;
}
................................................................................
pMem = sqlite3_malloc(szRegion);
if( pMem==0 ){
rc = SQLITE_NOMEM;
goto shmpage_out;
}
memset(pMem, 0, szRegion);
}
for(i=0; i<nShmPerMap; i++){
pShmNode->apRegion[pShmNode->nRegion+i] = &((char*)pMem)[szRegion*i];
}
pShmNode->nRegion += nShmPerMap;
}
}
shmpage_out:
if( pShmNode->nRegion>iRegion ){
*pp = pShmNode->apRegion[iRegion];
}else{
................................................................................
osMunmap(pFd->pMapRegion, pFd->mmapSizeActual);
pFd->pMapRegion = 0;
pFd->mmapSize = 0;
pFd->mmapSizeActual = 0;
}
}
/*
** Attempt to set the size of the memory mapping maintained by file
** descriptor pFd to nNew bytes. Any existing mapping is discarded.
**
** If successful, this function sets the following variables:
**
** unixFile.pMapRegion
................................................................................
assert( nNew>0 );
assert( pFd->mmapSizeActual>=pFd->mmapSize );
assert( MAP_FAILED!=0 );
if( (pFd->ctrlFlags & UNIXFILE_RDONLY)==0 ) flags |= PROT_WRITE;
if( pOrig ){
#if HAVE_MREMAP
i64 nReuse = pFd->mmapSize;
#else
const int szSyspage = unixGetPagesize();
i64 nReuse = (pFd->mmapSize & ~(szSyspage-1));
#endif
u8 *pReq = &pOrig[nReuse];
/* Unmap any pages of the existing mapping that cannot be reused. */
if( nReuse!=nOrig ){
osMunmap(pReq, nOrig-nReuse);
}
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