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Commitacd1536

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Up to now, SerializableSnapshot and QuerySnapshot are malloc'ed and
free'd for every transaction or statement, respectively. This patchputs these data structures into static memory, thus saving a few CPUcycles and two malloc calls per transaction or (in isolation levelREAD COMMITTED) per query.Manfred Koizar
1 parent752a4da commitacd1536

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3 files changed

+30
-33
lines changed

3 files changed

+30
-33
lines changed

‎src/backend/storage/ipc/sinval.c

Lines changed: 18 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.55 2003/05/27 17:49:46 momjian Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.56 2003/06/12 01:42:19 momjian Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -305,9 +305,8 @@ GetOldestXmin(bool allDbs)
305305
*----------
306306
*/
307307
Snapshot
308-
GetSnapshotData(boolserializable)
308+
GetSnapshotData(Snapshotsnapshot,boolserializable)
309309
{
310-
Snapshotsnapshot= (Snapshot)malloc(sizeof(SnapshotData));
311310
SISeg*segP=shmInvalBuffer;
312311
ProcState*stateP=segP->procState;
313312
TransactionIdxmin;
@@ -316,18 +315,29 @@ GetSnapshotData(bool serializable)
316315
intindex;
317316
intcount=0;
318317

319-
if (snapshot==NULL)
320-
elog(ERROR,"Memory exhausted in GetSnapshotData");
318+
Assert(snapshot!=NULL);
321319

322320
/*
323321
* Allocating space for MaxBackends xids is usually overkill;
324322
* lastBackend would be sufficient. But it seems better to do the
325323
* malloc while not holding the lock, so we can't look at lastBackend.
324+
*
325+
* if (snapshot->xip != NULL)
326+
* no need to free and reallocate xip;
327+
*
328+
* We can reuse the old xip array, because MaxBackends does not change
329+
* at runtime.
326330
*/
327-
snapshot->xip= (TransactionId*)
328-
malloc(MaxBackends*sizeof(TransactionId));
329331
if (snapshot->xip==NULL)
330-
elog(ERROR,"Memory exhausted in GetSnapshotData");
332+
{
333+
/*
334+
* First call for this snapshot
335+
*/
336+
snapshot->xip= (TransactionId*)
337+
malloc(MaxBackends*sizeof(TransactionId));
338+
if (snapshot->xip==NULL)
339+
elog(ERROR,"Memory exhausted in GetSnapshotData");
340+
}
331341

332342
globalxmin=xmin=GetCurrentTransactionId();
333343

‎src/backend/utils/time/tqual.c

Lines changed: 10 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,7 @@
1616
* Portions Copyright (c) 1994, Regents of the University of California
1717
*
1818
* IDENTIFICATION
19-
* $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.62 2003/02/23 23:20:52 tgl Exp $
19+
* $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.63 2003/06/12 01:42:20 momjian Exp $
2020
*
2121
*-------------------------------------------------------------------------
2222
*/
@@ -30,6 +30,8 @@
3030
staticSnapshotDataSnapshotDirtyData;
3131
SnapshotSnapshotDirty=&SnapshotDirtyData;
3232

33+
staticSnapshotDataQuerySnapshotData;
34+
staticSnapshotDataSerializableSnapshotData;
3335
SnapshotQuerySnapshot=NULL;
3436
SnapshotSerializableSnapshot=NULL;
3537

@@ -941,23 +943,16 @@ SetQuerySnapshot(void)
941943
/* 1st call in xaction? */
942944
if (SerializableSnapshot==NULL)
943945
{
944-
SerializableSnapshot=GetSnapshotData(true);
946+
SerializableSnapshot=GetSnapshotData(&SerializableSnapshotData,true);
945947
QuerySnapshot=SerializableSnapshot;
946948
Assert(QuerySnapshot!=NULL);
947949
return;
948950
}
949951

950-
if (QuerySnapshot!=SerializableSnapshot)
951-
{
952-
free(QuerySnapshot->xip);
953-
free(QuerySnapshot);
954-
QuerySnapshot=NULL;
955-
}
956-
957952
if (XactIsoLevel==XACT_SERIALIZABLE)
958953
QuerySnapshot=SerializableSnapshot;
959954
else
960-
QuerySnapshot=GetSnapshotData(false);
955+
QuerySnapshot=GetSnapshotData(&QuerySnapshotData,false);
961956

962957
Assert(QuerySnapshot!=NULL);
963958
}
@@ -1003,19 +998,11 @@ CopyQuerySnapshot(void)
1003998
void
1004999
FreeXactSnapshot(void)
10051000
{
1006-
if (QuerySnapshot!=NULL&&QuerySnapshot!=SerializableSnapshot)
1007-
{
1008-
free(QuerySnapshot->xip);
1009-
free(QuerySnapshot);
1010-
}
1011-
1001+
/*
1002+
* We do not free(QuerySnapshot->xip);
1003+
* or free(SerializableSnapshot->xip);
1004+
* they will be reused soon
1005+
*/
10121006
QuerySnapshot=NULL;
1013-
1014-
if (SerializableSnapshot!=NULL)
1015-
{
1016-
free(SerializableSnapshot->xip);
1017-
free(SerializableSnapshot);
1018-
}
1019-
10201007
SerializableSnapshot=NULL;
10211008
}

‎src/include/utils/tqual.h

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
99
* Portions Copyright (c) 1994, Regents of the University of California
1010
*
11-
* $Id: tqual.h,v 1.44 2003/02/23 23:20:52 tgl Exp $
11+
* $Id: tqual.h,v 1.45 2003/06/12 01:42:21 momjian Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -113,7 +113,7 @@ extern int HeapTupleSatisfiesUpdate(HeapTuple tuple,
113113
externHTSV_ResultHeapTupleSatisfiesVacuum(HeapTupleHeadertuple,
114114
TransactionIdOldestXmin);
115115

116-
externSnapshotGetSnapshotData(boolserializable);
116+
externSnapshotGetSnapshotData(Snapshotsnapshot,boolserializable);
117117
externvoidSetQuerySnapshot(void);
118118
externSnapshotCopyQuerySnapshot(void);
119119
externvoidFreeXactSnapshot(void);

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