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Avoid corner cases where aset.c would unnecessarily make malloc()

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requests of sizes that aren't powers of 2.  Per observation from
David Schultz, 28-Aug.
This commit is contained in:
Tom Lane 2003-09-13 22:25:38 +00:00
parent c472b8366f
commit 4cf6e9e081
1 changed files with 15 additions and 18 deletions
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33
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 1.52 2003/08/04 02:40:08 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/mmgr/aset.c,v 1.53 2003/09/13 22:25:38 tgl Exp $
*
* NOTE:
* This is a new (Feb. 05, 1999) implementation of the allocation set
@ -650,32 +650,29 @@ AllocSetAlloc(MemoryContext context, Size size)
}
else
{
/* Get size of prior block */
blksize = set->blocks->endptr - ((char *) set->blocks);
/*
* Special case: if very first allocation was for a large
* chunk (or we have a small "keeper" block), could have an
* undersized top block. Do something reasonable.
* Use first power of 2 that is larger than previous block,
* but not more than the allowed limit. (We don't simply double
* the prior block size, because in some cases this could be a
* funny size, eg if very first allocation was for an odd-sized
* large chunk.)
*/
if (blksize < set->initBlockSize)
blksize = set->initBlockSize;
else
{
/* Crank it up, but not past max */
Size pblksize = set->blocks->endptr - ((char *) set->blocks);
blksize = set->initBlockSize;
while (blksize <= pblksize)
blksize <<= 1;
if (blksize > set->maxBlockSize)
blksize = set->maxBlockSize;
}
if (blksize > set->maxBlockSize)
blksize = set->maxBlockSize;
}
/*
* If initBlockSize is less than ALLOC_CHUNK_LIMIT, we could need
* more space...
* more space... but try to keep it a power of 2.
*/
required_size = chunk_size + ALLOC_BLOCKHDRSZ + ALLOC_CHUNKHDRSZ;
if (blksize < required_size)
blksize = required_size;
while (blksize < required_size)
blksize <<= 1;
/* Try to allocate it */
block = (AllocBlock) malloc(blksize);