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First attempt at reducing mutex contention in the unix VFS by providing

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a separate mutex for each unixInodeInfo object.

FossilOrigin-Name: f69afaf00a659cd768a863c5f4a1d527f01187e037240da0ada527cb52c5afe8
This commit is contained in:
drh
2018-07-23 21:10:37 +00:00
parent 1489785be5
commit da6dc2404a
3 changed files with 44 additions and 26 deletions
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51
src/os_unix.c
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@@ -1108,15 +1108,29 @@ struct unixFileId {
** A single inode can have multiple file descriptors, so each unixFile
** structure contains a pointer to an instance of this object and this
** object keeps a count of the number of unixFile pointing to it.
**
** Mutex rules:
**
** (1) The pLockMutex mutex must be held in order to read or write
** any of the locking fields:
** nShared, nLock, eFileLock, or bProcessLock
**
** (2) When nRef>0, then the following fields are unchanging and can
** be read (but not written) without holding any mutex:
** fileId, pLockMutex
**
** (3) With the exceptions above, all the fields may only be read
** or written while holding the global unixBigLock mutex.
*/
struct unixInodeInfo {
struct unixFileId fileId; /* The lookup key */
int nShared; /* Number of SHARED locks held */
unsigned char eFileLock; /* One of SHARED_LOCK, RESERVED_LOCK etc. */
unsigned char bProcessLock; /* An exclusive process lock is held */
sqlite3_mutex *pLockMutex; /* Hold this mutex for... */
int nShared; /* Number of SHARED locks held */
int nLock; /* Number of outstanding file locks */
unsigned char eFileLock; /* One of SHARED_LOCK, RESERVED_LOCK etc. */
unsigned char bProcessLock; /* An exclusive process lock is held */
int nRef; /* Number of pointers to this structure */
unixShmNode *pShmNode; /* Shared memory associated with this inode */
int nLock; /* Number of outstanding file locks */
UnixUnusedFd *pUnused; /* Unused file descriptors to close */
unixInodeInfo *pNext; /* List of all unixInodeInfo objects */
unixInodeInfo *pPrev; /* .... doubly linked */
@@ -1273,6 +1287,7 @@ static void releaseInodeInfo(unixFile *pFile){
assert( pInode->pNext->pPrev==pInode );
pInode->pNext->pPrev = pInode->pPrev;
}
sqlite3_mutex_free(pInode->pLockMutex);
sqlite3_free(pInode);
}
}
@@ -1358,6 +1373,7 @@ static int findInodeInfo(
}
memset(pInode, 0, sizeof(*pInode));
memcpy(&pInode->fileId, &fileId, sizeof(fileId));
pInode->pLockMutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
pInode->nRef = 1;
pInode->pNext = inodeList;
pInode->pPrev = 0;
@@ -1436,7 +1452,7 @@ static int unixCheckReservedLock(sqlite3_file *id, int *pResOut){
assert( pFile );
assert( pFile->eFileLock<=SHARED_LOCK );
unixEnterMutex(); /* Because pFile->pInode is shared across threads */
sqlite3_mutex_enter(pFile->pInode->pLockMutex);
/* Check if a thread in this process holds such a lock */
if( pFile->pInode->eFileLock>SHARED_LOCK ){
@@ -1461,7 +1477,7 @@ static int unixCheckReservedLock(sqlite3_file *id, int *pResOut){
}
#endif
unixLeaveMutex();
sqlite3_mutex_leave(pFile->pInode->pLockMutex);
OSTRACE(("TEST WR-LOCK %d %d %d (unix)\n", pFile->h, rc, reserved));
*pResOut = reserved;
@@ -1527,8 +1543,8 @@ static int osSetPosixAdvisoryLock(
static int unixFileLock(unixFile *pFile, struct flock *pLock){
int rc;
unixInodeInfo *pInode = pFile->pInode;
assert( unixMutexHeld() );
assert( pInode!=0 );
assert( sqlite3_mutex_held(pInode->pLockMutex) );
if( (pFile->ctrlFlags & (UNIXFILE_EXCL|UNIXFILE_RDONLY))==UNIXFILE_EXCL ){
if( pInode->bProcessLock==0 ){
struct flock lock;
@@ -1647,8 +1663,8 @@ static int unixLock(sqlite3_file *id, int eFileLock){
/* This mutex is needed because pFile->pInode is shared across threads
*/
unixEnterMutex();
pInode = pFile->pInode;
sqlite3_mutex_enter(pInode->pLockMutex);
/* If some thread using this PID has a lock via a different unixFile*
** handle that precludes the requested lock, return BUSY.
@@ -1791,7 +1807,7 @@ static int unixLock(sqlite3_file *id, int eFileLock){
}
end_lock:
unixLeaveMutex();
sqlite3_mutex_leave(pInode->pLockMutex);
OSTRACE(("LOCK %d %s %s (unix)\n", pFile->h, azFileLock(eFileLock),
rc==SQLITE_OK ? "ok" : "failed"));
return rc;
@@ -1839,8 +1855,8 @@ static int posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
if( pFile->eFileLock<=eFileLock ){
return SQLITE_OK;
}
unixEnterMutex();
pInode = pFile->pInode;
sqlite3_mutex_enter(pInode->pLockMutex);
assert( pInode->nShared!=0 );
if( pFile->eFileLock>SHARED_LOCK ){
assert( pInode->eFileLock==pFile->eFileLock );
@@ -1972,7 +1988,7 @@ static int posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
}
end_unlock:
unixLeaveMutex();
sqlite3_mutex_leave(pInode->pLockMutex);
if( rc==SQLITE_OK ) pFile->eFileLock = eFileLock;
return rc;
}
@@ -2771,8 +2787,7 @@ static int afpCheckReservedLock(sqlite3_file *id, int *pResOut){
*pResOut = 1;
return SQLITE_OK;
}
unixEnterMutex(); /* Because pFile->pInode is shared across threads */
sqlite3_mutex_enter(pFile->pInode->pLockMutex);
/* Check if a thread in this process holds such a lock */
if( pFile->pInode->eFileLock>SHARED_LOCK ){
reserved = 1;
@@ -2796,7 +2811,7 @@ static int afpCheckReservedLock(sqlite3_file *id, int *pResOut){
}
}
unixLeaveMutex();
sqlite3_mutex_leave(pFile->pInode->pLockMutex);
OSTRACE(("TEST WR-LOCK %d %d %d (afp)\n", pFile->h, rc, reserved));
*pResOut = reserved;
@@ -2859,8 +2874,8 @@ static int afpLock(sqlite3_file *id, int eFileLock){
/* This mutex is needed because pFile->pInode is shared across threads
*/
unixEnterMutex();
pInode = pFile->pInode;
sqlite3_mutex_enter(pInode->pLockMutex);
/* If some thread using this PID has a lock via a different unixFile*
** handle that precludes the requested lock, return BUSY.
@@ -2996,7 +3011,7 @@ static int afpLock(sqlite3_file *id, int eFileLock){
}
afp_end_lock:
unixLeaveMutex();
sqlite3_mutex_leave(pInode->pLockMutex);
OSTRACE(("LOCK %d %s %s (afp)\n", pFile->h, azFileLock(eFileLock),
rc==SQLITE_OK ? "ok" : "failed"));
return rc;
@@ -3028,8 +3043,8 @@ static int afpUnlock(sqlite3_file *id, int eFileLock) {
if( pFile->eFileLock<=eFileLock ){
return SQLITE_OK;
}
unixEnterMutex();
pInode = pFile->pInode;
sqlite3_mutex_enter(pInode->pLockMutex);
assert( pInode->nShared!=0 );
if( pFile->eFileLock>SHARED_LOCK ){
assert( pInode->eFileLock==pFile->eFileLock );
@@ -3104,7 +3119,7 @@ static int afpUnlock(sqlite3_file *id, int eFileLock) {
}
}
unixLeaveMutex();
sqlite3_mutex_leave(pInode->pLockMutex);
if( rc==SQLITE_OK ) pFile->eFileLock = eFileLock;
return rc;
}