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Up to now, SerializableSnapshot and QuerySnapshot are malloc'ed and

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free'd for every transaction or statement, respectively.  This patch
puts these data structures into static memory, thus saving a few CPU
cycles and two malloc calls per transaction or (in isolation level
READ COMMITTED) per query.

Manfred Koizar
This commit is contained in:
Bruce Momjian 2003-06-12 01:42:21 +00:00
parent 752a4dac50
commit acd1536d9f
3 changed files with 30 additions and 33 deletions
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26
src/backend/storage/ipc/sinval.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.55 2003/05/27 17:49:46 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.56 2003/06/12 01:42:19 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -305,9 +305,8 @@ GetOldestXmin(bool allDbs)
*----------
*/
Snapshot
GetSnapshotData(bool serializable)
GetSnapshotData(Snapshot snapshot, bool serializable)
{
Snapshot snapshot = (Snapshot) malloc(sizeof(SnapshotData));
SISeg *segP = shmInvalBuffer;
ProcState *stateP = segP->procState;
TransactionId xmin;
@ -316,18 +315,29 @@ GetSnapshotData(bool serializable)
int index;
int count = 0;
if (snapshot == NULL)
elog(ERROR, "Memory exhausted in GetSnapshotData");
Assert(snapshot != NULL);
/*
* Allocating space for MaxBackends xids is usually overkill;
* lastBackend would be sufficient. But it seems better to do the
* malloc while not holding the lock, so we can't look at lastBackend.
*
* if (snapshot->xip != NULL)
* no need to free and reallocate xip;
*
* We can reuse the old xip array, because MaxBackends does not change
* at runtime.
*/
snapshot->xip = (TransactionId *)
malloc(MaxBackends * sizeof(TransactionId));
if (snapshot->xip == NULL)
elog(ERROR, "Memory exhausted in GetSnapshotData");
{
/*
* First call for this snapshot
*/
snapshot->xip = (TransactionId *)
malloc(MaxBackends * sizeof(TransactionId));
if (snapshot->xip == NULL)
elog(ERROR, "Memory exhausted in GetSnapshotData");
}
globalxmin = xmin = GetCurrentTransactionId();

33
src/backend/utils/time/tqual.c
View File

@ -16,7 +16,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.62 2003/02/23 23:20:52 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.63 2003/06/12 01:42:20 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -30,6 +30,8 @@
static SnapshotData SnapshotDirtyData;
Snapshot SnapshotDirty = &SnapshotDirtyData;
static SnapshotData QuerySnapshotData;
static SnapshotData SerializableSnapshotData;
Snapshot QuerySnapshot = NULL;
Snapshot SerializableSnapshot = NULL;
@ -941,23 +943,16 @@ SetQuerySnapshot(void)
/* 1st call in xaction? */
if (SerializableSnapshot == NULL)
{
SerializableSnapshot = GetSnapshotData(true);
SerializableSnapshot = GetSnapshotData(&SerializableSnapshotData, true);
QuerySnapshot = SerializableSnapshot;
Assert(QuerySnapshot != NULL);
return;
}
if (QuerySnapshot != SerializableSnapshot)
{
free(QuerySnapshot->xip);
free(QuerySnapshot);
QuerySnapshot = NULL;
}
if (XactIsoLevel == XACT_SERIALIZABLE)
QuerySnapshot = SerializableSnapshot;
else
QuerySnapshot = GetSnapshotData(false);
QuerySnapshot = GetSnapshotData(&QuerySnapshotData, false);
Assert(QuerySnapshot != NULL);
}
@ -1003,19 +998,11 @@ CopyQuerySnapshot(void)
void
FreeXactSnapshot(void)
{
if (QuerySnapshot != NULL && QuerySnapshot != SerializableSnapshot)
{
free(QuerySnapshot->xip);
free(QuerySnapshot);
}
/*
* We do not free(QuerySnapshot->xip);
* or free(SerializableSnapshot->xip);
* they will be reused soon
*/
QuerySnapshot = NULL;
if (SerializableSnapshot != NULL)
{
free(SerializableSnapshot->xip);
free(SerializableSnapshot);
}
SerializableSnapshot = NULL;
}

4
src/include/utils/tqual.h
View File

@ -8,7 +8,7 @@
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: tqual.h,v 1.44 2003/02/23 23:20:52 tgl Exp $
* $Id: tqual.h,v 1.45 2003/06/12 01:42:21 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -113,7 +113,7 @@ extern int HeapTupleSatisfiesUpdate(HeapTuple tuple,
extern HTSV_Result HeapTupleSatisfiesVacuum(HeapTupleHeader tuple,
TransactionId OldestXmin);
extern Snapshot GetSnapshotData(bool serializable);
extern Snapshot GetSnapshotData(Snapshot snapshot, bool serializable);
extern void SetQuerySnapshot(void);
extern Snapshot CopyQuerySnapshot(void);
extern void FreeXactSnapshot(void);