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Alter AllocSet routines so that requests larger than

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ALLOC_BIGCHUNK_LIMIT are always allocated as separate malloc() blocks,
and are free()d immediately upon pfree().  Also, if such a chunk is enlarged
with repalloc(), translate the operation into a realloc() so as to
minimize memory usage.  Of course, these large chunks still get freed
automatically if the alloc set is reset.
I have set ALLOC_BIGCHUNK_LIMIT at 64K for now, but perhaps another
size would be better?
This commit is contained in:
Tom Lane
1999-08-24 20:11:19 +00:00
parent 1b81fd7793
commit 2b67dc5387
2 changed files with 171 additions and 69 deletions
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67
src/include/utils/memutils.h
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@ -15,7 +15,7 @@
*
* Copyright (c) 1994, Regents of the University of California
*
* $Id: memutils.h,v 1.30 1999/07/15 15:21:41 momjian Exp $
* $Id: memutils.h,v 1.31 1999/08/24 20:11:19 tgl Exp $
*
* NOTES
* some of the information in this file will be moved to
@ -101,6 +101,12 @@ extern void OrderedElemPushInto(OrderedElem elem, OrderedSet Set);
* reallocated. In addition, an allocation set may be reset which
* will cause all memory allocated within it to be freed.
*
* XXX The following material about allocation modes is all OUT OF DATE.
* aset.c currently implements only one allocation strategy,
* DynamicAllocMode, and that's the only one anyone ever requests anyway.
* If we ever did have more strategies, the new ones might or might
* not look like what is described here...
*
* Allocations may occur in four different modes. The mode of
* allocation does not affect the behavior of allocations except in
* terms of performance. The allocation mode is set at the time of
@ -146,7 +152,7 @@ typedef Pointer AllocPointer;
* Mode of allocation for an allocation set.
*
* Note:
* See above for a description of the various nodes.
* See above for a description of the various modes.
*/
typedef enum AllocMode
{
@ -158,23 +164,42 @@ typedef enum AllocMode
#define DefaultAllocMode DynamicAllocMode
typedef struct AllocSetData *AllocSet;
typedef struct AllocBlockData *AllocBlock;
typedef struct AllocChunkData *AllocChunk;
/*
* AllocSet
* Allocation set.
*/
typedef struct AllocSetData
{
AllocBlock blocks; /* head of list of blocks in this set */
#define ALLOCSET_NUM_FREELISTS 8
AllocChunk freelist[ALLOCSET_NUM_FREELISTS]; /* free chunk lists */
/* Note: this will change in the future to support other modes */
} AllocSetData;
/*
* AllocBlock
* Small pieces of memory are taken from bigger blocks of
* memory with a size aligned to a power of two. These
* pieces are not free's separately, instead they are reused
* for the next allocation of a fitting size.
* An AllocBlock is the unit of memory that is obtained by aset.c
* from malloc(). It contains one or more AllocChunks, which are
* the units requested by palloc() and freed by pfree(). AllocChunks
* cannot be returned to malloc() individually, instead they are put
* on freelists by pfree() and re-used by the next palloc() that has
* a matching request size.
*
* AllocBlockData is the header data for a block --- the usable space
* within the block begins at the next alignment boundary.
*/
typedef struct AllocBlockData
{
struct AllocSetData *aset;
struct AllocBlockData *next;
char *freeptr;
char *endptr;
AllocSet aset; /* aset that owns this block */
AllocBlock next; /* next block in aset's blocks list */
char *freeptr; /* start of free space in this block */
char *endptr; /* end of space in this block */
} AllocBlockData;
typedef AllocBlockData *AllocBlock;
/*
* AllocChunk
* The prefix of each piece of memory in an AllocBlock
@ -183,26 +208,10 @@ typedef struct AllocChunkData
{
/* aset is the owning aset if allocated, or the freelist link if free */
void *aset;
/* size is always the chunk size */
/* size is always the size of the usable space in the chunk */
Size size;
} AllocChunkData;
typedef AllocChunkData *AllocChunk;
/*
* AllocSet
* Allocation set.
*/
typedef struct AllocSetData
{
struct AllocBlockData *blocks;
#define ALLOCSET_NUM_FREELISTS 8
struct AllocChunkData *freelist[ALLOCSET_NUM_FREELISTS];
/* Note: this will change in the future to support other modes */
} AllocSetData;
typedef AllocSetData *AllocSet;
/*
* AllocPointerIsValid
* True iff pointer is valid allocation pointer.