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Commita635ab4

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committed
Short-circuit AllocSetReset if nothing has been palloc'd in the memory
context since the previous AllocSetReset. Original patch by Atsushi Ogawa,editorialized on a little bit by Tom Lane.
1 parent91a21b5 commita635ab4

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1 file changed

+35
-13
lines changed

1 file changed

+35
-13
lines changed

‎src/backend/utils/mmgr/aset.c

Lines changed: 35 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,7 @@
1111
* Portions Copyright (c) 1994, Regents of the University of California
1212
*
1313
* IDENTIFICATION
14-
* $PostgreSQL: pgsql/src/backend/utils/mmgr/aset.c,v 1.62 2005/06/04 22:57:22 momjian Exp $
14+
* $PostgreSQL: pgsql/src/backend/utils/mmgr/aset.c,v 1.63 2005/09/01 18:15:42 tgl Exp $
1515
*
1616
* NOTE:
1717
*This is a new (Feb. 05, 1999) implementation of the allocation set
@@ -123,13 +123,20 @@ typedef void *AllocPointer;
123123

124124
/*
125125
* AllocSetContext is our standard implementation of MemoryContext.
126+
*
127+
* Note: isReset means there is nothing for AllocSetReset to do. This is
128+
* different from the aset being physically empty (empty blocks list) because
129+
* we may still have a keeper block. It's also different from the set being
130+
* logically empty, because we don't attempt to detect pfree'ing the last
131+
* active chunk.
126132
*/
127133
typedefstructAllocSetContext
128134
{
129135
MemoryContextDataheader;/* Standard memory-context fields */
130136
/* Info about storage allocated in this context: */
131137
AllocBlockblocks;/* head of list of blocks in this set */
132138
AllocChunkfreelist[ALLOCSET_NUM_FREELISTS];/* free chunk lists */
139+
boolisReset;/* T = no space alloced since last reset */
133140
/* Allocation parameters for this context: */
134141
SizeinitBlockSize;/* initial block size */
135142
SizemaxBlockSize;/* maximum block size */
@@ -347,6 +354,8 @@ AllocSetContextCreate(MemoryContext parent,
347354
context->keeper=block;
348355
}
349356

357+
context->isReset= true;
358+
350359
return (MemoryContext)context;
351360
}
352361

@@ -386,26 +395,28 @@ static void
386395
AllocSetReset(MemoryContextcontext)
387396
{
388397
AllocSetset= (AllocSet)context;
389-
AllocBlockblock=set->blocks;
398+
AllocBlockblock;
390399

391400
AssertArg(AllocSetIsValid(set));
392401

402+
/* Nothing to do if no pallocs since startup or last reset */
403+
if (set->isReset)
404+
return;
405+
393406
#ifdefMEMORY_CONTEXT_CHECKING
394407
/* Check for corruption and leaks before freeing */
395408
AllocSetCheck(context);
396409
#endif
397410

398-
/* Nothing to do if context has never contained any data */
399-
if (block==NULL)
400-
return;
401-
402411
/* Clear chunk freelists */
403412
MemSetAligned(set->freelist,0,sizeof(set->freelist));
404413

414+
block=set->blocks;
415+
405416
/* New blocks list is either empty or just the keeper block */
406417
set->blocks=set->keeper;
407418

408-
do
419+
while (block!=NULL)
409420
{
410421
AllocBlocknext=block->next;
411422

@@ -432,7 +443,8 @@ AllocSetReset(MemoryContext context)
432443
}
433444
block=next;
434445
}
435-
while (block!=NULL);
446+
447+
set->isReset= true;
436448
}
437449

438450
/*
@@ -538,6 +550,8 @@ AllocSetAlloc(MemoryContext context, Size size)
538550
set->blocks=block;
539551
}
540552

553+
set->isReset= false;
554+
541555
AllocAllocInfo(set,chunk);
542556
returnAllocChunkGetPointer(chunk);
543557
}
@@ -576,6 +590,9 @@ AllocSetAlloc(MemoryContext context, Size size)
576590
((char*)AllocChunkGetPointer(chunk))[size]=0x7E;
577591
#endif
578592

593+
/* isReset must be false already */
594+
Assert(!set->isReset);
595+
579596
AllocAllocInfo(set,chunk);
580597
returnAllocChunkGetPointer(chunk);
581598
}
@@ -748,6 +765,8 @@ AllocSetAlloc(MemoryContext context, Size size)
748765
((char*)AllocChunkGetPointer(chunk))[size]=0x7E;
749766
#endif
750767

768+
set->isReset= false;
769+
751770
AllocAllocInfo(set,chunk);
752771
returnAllocChunkGetPointer(chunk);
753772
}
@@ -846,6 +865,9 @@ AllocSetRealloc(MemoryContext context, void *pointer, Size size)
846865
set->header.name,chunk);
847866
#endif
848867

868+
/* isReset must be false already */
869+
Assert(!set->isReset);
870+
849871
/*
850872
* Chunk sizes are aligned to power of 2 in AllocSetAlloc(). Maybe the
851873
* allocated area already is >= the new size. (In particular, we
@@ -1009,12 +1031,12 @@ AllocSetIsEmpty(MemoryContext context)
10091031
AllocSetset= (AllocSet)context;
10101032

10111033
/*
1012-
* For now, we say "empty" only if the contextnever contained any
1013-
*space at all.We could examine the freelists to determine if all
1014-
*space has beenfreed, but it's not really worth the trouble for
1015-
*present uses ofthis functionality.
1034+
* For now, we say "empty" only if the contextis new or just reset.
1035+
* We could examine the freelists to determine if all space has been
1036+
* freed, but it's not really worth the trouble for present uses of
1037+
* this functionality.
10161038
*/
1017-
if (set->blocks==NULL)
1039+
if (set->isReset)
10181040
return true;
10191041
return false;
10201042
}

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