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Keep track of the last active slot in the shared ProcState array, so

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that search loops only have to scan that far and not through all maxBackends
entries.  This eliminates a performance penalty for setting maxBackends
much higher than the average number of active backends.  Also, eliminate
no-longer-used 'backend tag' concept.  Remove setting of environment
variables at backend start (except for CYR_RECODE), since none of them
are being examined by the backend any longer.
This commit is contained in:
Tom Lane
2000-11-12 20:51:52 +00:00
parent c48025e799
commit ebb0a20149
10 changed files with 153 additions and 235 deletions
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24
src/backend/storage/ipc/sinval.c
View File

@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.22 2000/11/05 22:50:20 vadim Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.23 2000/11/12 20:51:51 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -185,6 +185,9 @@ void
/*
* DatabaseHasActiveBackends -- are there any backends running in the given DB
*
* If 'ignoreMyself' is TRUE, ignore this particular backend while checking
* for backends in the target database.
*
* This function is used to interlock DROP DATABASE against there being
* any active backends in the target DB --- dropping the DB while active
* backends remain would be a Bad Thing. Note that we cannot detect here
@@ -194,7 +197,7 @@ void
*/
bool
DatabaseHasActiveBackends(Oid databaseId)
DatabaseHasActiveBackends(Oid databaseId, bool ignoreMyself)
{
bool result = false;
SISeg *segP = shmInvalBuffer;
@@ -203,7 +206,7 @@ DatabaseHasActiveBackends(Oid databaseId)
SpinAcquire(SInvalLock);
for (index = 0; index < segP->maxBackends; index++)
for (index = 0; index < segP->lastBackend; index++)
{
SHMEM_OFFSET pOffset = stateP[index].procStruct;
@@ -213,6 +216,9 @@ DatabaseHasActiveBackends(Oid databaseId)
if (proc->databaseId == databaseId)
{
if (ignoreMyself && proc == MyProc)
continue;
result = true;
break;
}
@@ -237,7 +243,7 @@ TransactionIdIsInProgress(TransactionId xid)
SpinAcquire(SInvalLock);
for (index = 0; index < segP->maxBackends; index++)
for (index = 0; index < segP->lastBackend; index++)
{
SHMEM_OFFSET pOffset = stateP[index].procStruct;
@@ -275,7 +281,7 @@ GetXmaxRecent(TransactionId *XmaxRecent)
SpinAcquire(SInvalLock);
for (index = 0; index < segP->maxBackends; index++)
for (index = 0; index < segP->lastBackend; index++)
{
SHMEM_OFFSET pOffset = stateP[index].procStruct;
@@ -309,11 +315,11 @@ GetSnapshotData(bool serializable)
int count = 0;
/*
* There can be no more than maxBackends active transactions, so this
* There can be no more than lastBackend active transactions, so this
* is enough space:
*/
snapshot->xip = (TransactionId *)
malloc(segP->maxBackends * sizeof(TransactionId));
malloc(segP->lastBackend * sizeof(TransactionId));
snapshot->xmin = GetCurrentTransactionId();
SpinAcquire(SInvalLock);
@@ -326,7 +332,7 @@ GetSnapshotData(bool serializable)
*/
ReadNewTransactionId(&(snapshot->xmax));
for (index = 0; index < segP->maxBackends; index++)
for (index = 0; index < segP->lastBackend; index++)
{
SHMEM_OFFSET pOffset = stateP[index].procStruct;
@@ -386,7 +392,7 @@ GetUndoRecPtr(void)
SpinAcquire(SInvalLock);
for (index = 0; index < segP->maxBackends; index++)
for (index = 0; index < segP->lastBackend; index++)
{
SHMEM_OFFSET pOffset = stateP[index].procStruct;

65
src/backend/storage/ipc/sinvaladt.c
View File

@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinvaladt.c,v 1.34 2000/10/02 21:45:32 petere Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinvaladt.c,v 1.35 2000/11/12 20:51:51 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -117,6 +117,7 @@ SISegInit(SISeg *segP, int maxBackends)
/* Clear message counters, save size of procState array */
segP->minMsgNum = 0;
segP->maxMsgNum = 0;
segP->lastBackend = 0;
segP->maxBackends = maxBackends;
/* The buffer[] array is initially all unused, so we need not fill it */
@@ -126,7 +127,6 @@ SISegInit(SISeg *segP, int maxBackends)
{
segP->procState[i].nextMsgNum = -1; /* inactive */
segP->procState[i].resetState = false;
segP->procState[i].tag = InvalidBackendTag;
segP->procState[i].procStruct = INVALID_OFFSET;
}
}
@@ -145,47 +145,45 @@ SIBackendInit(SISeg *segP)
int index;
ProcState *stateP = NULL;
Assert(MyBackendTag > 0);
/* Check for duplicate backend tags (should never happen) */
for (index = 0; index < segP->maxBackends; index++)
{
if (segP->procState[index].tag == MyBackendTag)
elog(FATAL, "SIBackendInit: tag %d already in use", MyBackendTag);
}
/* Look for a free entry in the procState array */
for (index = 0; index < segP->maxBackends; index++)
for (index = 0; index < segP->lastBackend; index++)
{
if (segP->procState[index].tag == InvalidBackendTag)
if (segP->procState[index].nextMsgNum < 0) /* inactive slot? */
{
stateP = &segP->procState[index];
break;
}
}
/*
* elog() with spinlock held is probably not too cool, but this
* condition should never happen anyway.
*/
if (stateP == NULL)
{
elog(NOTICE, "SIBackendInit: no free procState slot available");
MyBackendId = InvalidBackendTag;
return 0;
if (segP->lastBackend < segP->maxBackends)
{
stateP = &segP->procState[segP->lastBackend];
Assert(stateP->nextMsgNum < 0);
segP->lastBackend++;
}
else
{
/*
* elog() with spinlock held is probably not too cool, but this
* condition should never happen anyway.
*/
elog(NOTICE, "SIBackendInit: no free procState slot available");
MyBackendId = InvalidBackendId;
return 0;
}
}
MyBackendId = (stateP - &segP->procState[0]) + 1;
#ifdef INVALIDDEBUG
elog(DEBUG, "SIBackendInit: backend tag %d; backend id %d.",
MyBackendTag, MyBackendId);
elog(DEBUG, "SIBackendInit: backend id %d", MyBackendId);
#endif /* INVALIDDEBUG */
/* mark myself active, with all extant messages already read */
stateP->nextMsgNum = segP->maxMsgNum;
stateP->resetState = false;
stateP->tag = MyBackendTag;
stateP->procStruct = MAKE_OFFSET(MyProc);
/* register exit routine to mark my entry inactive at exit */
@@ -206,17 +204,26 @@ SIBackendInit(SISeg *segP)
static void
CleanupInvalidationState(int status, Datum arg)
{
SISeg *segP = (void*) DatumGetPointer(arg);
SISeg *segP = (SISeg *) DatumGetPointer(arg);
int i;
Assert(PointerIsValid(segP));
SpinAcquire(SInvalLock);
/* Mark myself inactive */
segP->procState[MyBackendId - 1].nextMsgNum = -1;
segP->procState[MyBackendId - 1].resetState = false;
segP->procState[MyBackendId - 1].tag = InvalidBackendTag;
segP->procState[MyBackendId - 1].procStruct = INVALID_OFFSET;
/* Recompute index of last active backend */
for (i = segP->lastBackend; i > 0; i--)
{
if (segP->procState[i - 1].nextMsgNum >= 0)
break;
}
segP->lastBackend = i;
SpinRelease(SInvalLock);
}
@@ -299,7 +306,7 @@ SISetProcStateInvalid(SISeg *segP)
segP->minMsgNum = 0;
segP->maxMsgNum = 0;
for (i = 0; i < segP->maxBackends; i++)
for (i = 0; i < segP->lastBackend; i++)
{
if (segP->procState[i].nextMsgNum >= 0) /* active backend? */
{
@@ -325,8 +332,6 @@ SIGetDataEntry(SISeg *segP, int backendId,
{
ProcState *stateP = &segP->procState[backendId - 1];
Assert(stateP->tag == MyBackendTag);
if (stateP->resetState)
{
@@ -373,7 +378,7 @@ SIDelExpiredDataEntries(SISeg *segP)
/* Recompute minMsgNum = minimum of all backends' nextMsgNum */
for (i = 0; i < segP->maxBackends; i++)
for (i = 0; i < segP->lastBackend; i++)
{
h = segP->procState[i].nextMsgNum;
if (h >= 0)
@@ -392,7 +397,7 @@ SIDelExpiredDataEntries(SISeg *segP)
{
segP->minMsgNum -= MSGNUMWRAPAROUND;
segP->maxMsgNum -= MSGNUMWRAPAROUND;
for (i = 0; i < segP->maxBackends; i++)
for (i = 0; i < segP->lastBackend; i++)
{
if (segP->procState[i].nextMsgNum >= 0)
segP->procState[i].nextMsgNum -= MSGNUMWRAPAROUND;