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Tom Lane <tgl@sss.pgh.pa.us> writes:

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> a_ogawa <a_ogawa@hi-ho.ne.jp> writes:
> > It is a reasonable idea. However, the majority part of MemSet was not
> > able to be avoided by this idea. Because the per-tuple contexts are used
> > at the early stage of executor.
>
> Drat.  Well, what about changing that?  We could introduce additional
> contexts or change the startup behavior so that the ones that are
> frequently reset don't have any data in them unless you are working
> with pass-by-ref values inside the inner loop.

That might be possible. However, I think that we should change only
aset.c about this article.
I thought further: We can check whether context was used from the last
reset even when blocks list is not empty. Please see attached patch.

The effect of the patch that I measured is as follows:

o Execution time that executed the SQL ten times.
(1)Linux(CPU: Pentium III, Compiler option: -O2)
 - original: 24.960s
 - patched : 23.114s

(2)Linux(CPU: Pentium 4, Compiler option: -O2)
 - original: 8.730s
 - patched : 7.962s

(3)Solaris(CPU: Ultra SPARC III, Compiler option: -O2)
 - original: 37.0s
 - patched : 33.7s

Atsushi Ogawa (a_ogawa)
This commit is contained in:
Bruce Momjian 2005-06-04 20:14:12 +00:00
parent e18e8f8735
commit 3cf1fd3263
1 changed files with 12 additions and 1 deletions
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13
src/backend/utils/mmgr/aset.c
View File

@ -11,7 +11,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/mmgr/aset.c,v 1.60 2005/05/14 20:29:13 tgl Exp $
* $PostgreSQL: pgsql/src/backend/utils/mmgr/aset.c,v 1.61 2005/06/04 20:14:12 momjian Exp $
*
* NOTE:
* This is a new (Feb. 05, 1999) implementation of the allocation set
@ -399,6 +399,17 @@ AllocSetReset(MemoryContext context)
if (block == NULL)
return;
/*
* When blocks list has only "keeper" block and freeptr of the block
* is initial value, the context is not used from last reset.
*/
if (block == set->keeper && block->next == NULL)
{
char *datastart = ((char *) block) + ALLOC_BLOCKHDRSZ;
if (block->freeptr == datastart)
return;
}
/* Clear chunk freelists */
MemSetAligned(set->freelist, 0, sizeof(set->freelist));