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Tweak default memory context allocation policy so that a context is not

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given any malloc block until something is first allocated in it; but
thereafter, MemoryContextReset won't release that first malloc block.
This preserves the quick-reset property of the original policy, without
forcing 8K to be allocated to every context whether any of it is ever
used or not.  Also, remove some more no-longer-needed explicit freeing
during ExecEndPlan.
This commit is contained in:
Tom Lane
2002-12-15 21:01:34 +00:00
parent 5bab36e9f6
commit e64c7feb2f
11 changed files with 66 additions and 99 deletions
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26
src/backend/utils/mmgr/aset.c
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@@ -11,7 +11,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/mmgr/aset.c,v 1.48 2002/09/04 20:31:33 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/mmgr/aset.c,v 1.49 2002/12/15 21:01:34 tgl Exp $
*
* NOTE:
* This is a new (Feb. 05, 1999) implementation of the allocation set
@@ -371,10 +371,11 @@ AllocSetInit(MemoryContext context)
* Frees all memory which is allocated in the given set.
*
* Actually, this routine has some discretion about what to do.
* It should mark all allocated chunks freed, but it need not
* necessarily give back all the resources the set owns. Our
* actual implementation is that we hang on to any "keeper"
* block specified for the set.
* It should mark all allocated chunks freed, but it need not necessarily
* give back all the resources the set owns. Our actual implementation is
* that we hang onto any "keeper" block specified for the set. In this way,
* we don't thrash malloc() when a context is repeatedly reset after small
* allocations, which is typical behavior for per-tuple contexts.
*/
static void
AllocSetReset(MemoryContext context)
@@ -697,6 +698,21 @@ AllocSetAlloc(MemoryContext context, Size size)
block->freeptr = ((char *) block) + ALLOC_BLOCKHDRSZ;
block->endptr = ((char *) block) + blksize;
/*
* If this is the first block of the set, make it the "keeper" block.
* Formerly, a keeper block could only be created during context
* creation, but allowing it to happen here lets us have fast reset
* cycling even for contexts created with minContextSize = 0; that
* way we don't have to force space to be allocated in contexts that
* might never need any space. Don't mark an oversize block as
* a keeper, however.
*/
if (set->blocks == NULL && blksize == set->initBlockSize)
{
Assert(set->keeper == NULL);
set->keeper = block;
}
block->next = set->blocks;
set->blocks = block;
}

4
src/backend/utils/mmgr/mcxt.c
View File

@@ -14,7 +14,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/mmgr/mcxt.c,v 1.36 2002/11/13 00:37:06 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/mmgr/mcxt.c,v 1.37 2002/12/15 21:01:34 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -80,7 +80,7 @@ MemoryContextInit(void)
*/
TopMemoryContext = AllocSetContextCreate((MemoryContext) NULL,
"TopMemoryContext",
8 * 1024,
0,
8 * 1024,
8 * 1024);