Here we reduce the block size fields in AllocSetContext, GenerationContext
and SlabContext from Size down to uint32. Ever since
c6e0fe1f2, blocks
for non-dedicated palloc chunks can no longer be larger than 1GB, so
there's no need to store the various block size fields as 64-bit values.
32 bits are enough to store 2^30.
Here we also further reduce the memory context struct sizes by getting rid
of the 'keeper' field which stores a pointer to the context's keeper
block. All the context types which have this field always allocate the
keeper block in the same allocation as the memory context itself, so the
keeper block always comes right at the end of the context struct. Add
some macros to calculate that address rather than storing it in the
context.
Overall, in AllocSetContext and GenerationContext, this saves 20 bytes on
64-bit builds which for ALLOCSET_SMALL_SIZES can sometimes mean the
difference between having to allocate a 2nd block and storing all the
required allocations on the keeper block alone. Such contexts are used
in relcache to store cache entries for indexes, of which there can be
a large number in a single backend.
Author: Melih Mutlu
Reviewed-by: David Rowley
Discussion: https://postgr.es/m/CAGPVpCSOW3uJ1QJmsMR9_oE3X7fG_z4q0AoU4R_w+2RzvroPFg@mail.gmail.com
AllocBlock blocks; /* head of list of blocks in this set */
MemoryChunk *freelist[ALLOCSET_NUM_FREELISTS]; /* free chunk lists */
/* Allocation parameters for this context: */
- Size initBlockSize; /* initial block size */
- Size maxBlockSize; /* maximum block size */
- Size nextBlockSize; /* next block size to allocate */
- Size allocChunkLimit; /* effective chunk size limit */
- AllocBlock keeper; /* keep this block over resets */
+ uint32 initBlockSize; /* initial block size */
+ uint32 maxBlockSize; /* maximum block size */
+ uint32 nextBlockSize; /* next block size to allocate */
+ uint32 allocChunkLimit; /* effective chunk size limit */
/* freelist this context could be put in, or -1 if not a candidate: */
int freeListIndex; /* index in context_freelists[], or -1 */
} AllocSetContext;
*/
#define MAX_FREE_CONTEXTS 100 /* arbitrary limit on freelist length */
+/* Obtain the keeper block for an allocation set */
+#define KeeperBlock(set) \
+ ((AllocBlock) (((char *) set) + MAXALIGN(sizeof(AllocSetContext))))
+
+/* Check if the block is the keeper block of the given allocation set */
+#define IsKeeperBlock(set, block) ((block) == (KeeperBlock(set)))
+
typedef struct AllocSetFreeList
{
int num_free; /* current list length */
name);
((MemoryContext) set)->mem_allocated =
- set->keeper->endptr - ((char *) set);
+ KeeperBlock(set)->endptr - ((char *) set);
return (MemoryContext) set;
}
*/
/* Fill in the initial block's block header */
- block = (AllocBlock) (((char *) set) + MAXALIGN(sizeof(AllocSetContext)));
+ block = KeeperBlock(set);
block->aset = set;
block->freeptr = ((char *) block) + ALLOC_BLOCKHDRSZ;
block->endptr = ((char *) set) + firstBlockSize;
/* Remember block as part of block list */
set->blocks = block;
- /* Mark block as not to be released at reset time */
- set->keeper = block;
/* Finish filling in aset-specific parts of the context header */
MemSetAligned(set->freelist, 0, sizeof(set->freelist));
- set->initBlockSize = initBlockSize;
- set->maxBlockSize = maxBlockSize;
- set->nextBlockSize = initBlockSize;
+ set->initBlockSize = (uint32) initBlockSize;
+ set->maxBlockSize = (uint32) maxBlockSize;
+ set->nextBlockSize = (uint32) initBlockSize;
set->freeListIndex = freeListIndex;
/*
#endif
/* Remember keeper block size for Assert below */
- keepersize = set->keeper->endptr - ((char *) set);
+ keepersize = KeeperBlock(set)->endptr - ((char *) set);
/* Clear chunk freelists */
MemSetAligned(set->freelist, 0, sizeof(set->freelist));
block = set->blocks;
/* New blocks list will be just the keeper block */
- set->blocks = set->keeper;
+ set->blocks = KeeperBlock(set);
while (block != NULL)
{
AllocBlock next = block->next;
- if (block == set->keeper)
+ if (IsKeeperBlock(set, block))
{
/* Reset the block, but don't return it to malloc */
char *datastart = ((char *) block) + ALLOC_BLOCKHDRSZ;
#endif
/* Remember keeper block size for Assert below */
- keepersize = set->keeper->endptr - ((char *) set);
+ keepersize = KeeperBlock(set)->endptr - ((char *) set);
/*
* If the context is a candidate for a freelist, put it into that freelist
{
AllocBlock next = block->next;
- if (block != set->keeper)
+ if (!IsKeeperBlock(set, block))
context->mem_allocated -= block->endptr - ((char *) block);
#ifdef CLOBBER_FREED_MEMORY
wipe_mem(block, block->freeptr - ((char *) block));
#endif
- if (block != set->keeper)
+ if (!IsKeeperBlock(set, block))
free(block);
block = next;
long nchunks = 0;
bool has_external_chunk = false;
- if (set->keeper == block)
+ if (IsKeeperBlock(set, block))
total_allocated += block->endptr - ((char *) set);
else
total_allocated += block->endptr - ((char *) block);
*/
if (!blk_used)
{
- if (set->keeper != block)
+ if (!IsKeeperBlock(set, block))
elog(WARNING, "problem in alloc set %s: empty block %p",
name, block);
}
MemoryContextData header; /* Standard memory-context fields */
/* Generational context parameters */
- Size initBlockSize; /* initial block size */
- Size maxBlockSize; /* maximum block size */
- Size nextBlockSize; /* next block size to allocate */
- Size allocChunkLimit; /* effective chunk size limit */
+ uint32 initBlockSize; /* initial block size */
+ uint32 maxBlockSize; /* maximum block size */
+ uint32 nextBlockSize; /* next block size to allocate */
+ uint32 allocChunkLimit; /* effective chunk size limit */
GenerationBlock *block; /* current (most recently allocated) block, or
* NULL if we've just freed the most recent
* block */
GenerationBlock *freeblock; /* pointer to a block that's being recycled,
* or NULL if there's no such block. */
- GenerationBlock *keeper; /* keep this block over resets */
dlist_head blocks; /* list of blocks */
} GenerationContext;
#define ExternalChunkGetBlock(chunk) \
(GenerationBlock *) ((char *) chunk - Generation_BLOCKHDRSZ)
+/* Obtain the keeper block for a generation context */
+#define KeeperBlock(set) \
+ ((GenerationBlock *) (((char *) set) + \
+ MAXALIGN(sizeof(GenerationContext))))
+
+/* Check if the block is the keeper block of the given generation context */
+#define IsKeeperBlock(set, block) ((block) == (KeeperBlock(set)))
+
/* Inlined helper functions */
static inline void GenerationBlockInit(GenerationContext *context,
GenerationBlock *block,
dlist_init(&set->blocks);
/* Fill in the initial block's block header */
- block = (GenerationBlock *) (((char *) set) + MAXALIGN(sizeof(GenerationContext)));
+ block = KeeperBlock(set);
/* determine the block size and initialize it */
firstBlockSize = allocSize - MAXALIGN(sizeof(GenerationContext));
GenerationBlockInit(set, block, firstBlockSize);
/* No free block, yet */
set->freeblock = NULL;
- /* Mark block as not to be released at reset time */
- set->keeper = block;
-
/* Fill in GenerationContext-specific header fields */
- set->initBlockSize = initBlockSize;
- set->maxBlockSize = maxBlockSize;
- set->nextBlockSize = initBlockSize;
+ set->initBlockSize = (uint32) initBlockSize;
+ set->maxBlockSize = (uint32) maxBlockSize;
+ set->nextBlockSize = (uint32) initBlockSize;
/*
* Compute the allocation chunk size limit for this context.
{
GenerationBlock *block = dlist_container(GenerationBlock, node, miter.cur);
- if (block == set->keeper)
+ if (IsKeeperBlock(set, block))
GenerationBlockMarkEmpty(block);
else
GenerationBlockFree(set, block);
}
/* set it so new allocations to make use of the keeper block */
- set->block = set->keeper;
+ set->block = KeeperBlock(set);
/* Reset block size allocation sequence, too */
set->nextBlockSize = set->initBlockSize;
*/
set->freeblock = NULL;
}
- else if (GenerationBlockIsEmpty(set->keeper) &&
- GenerationBlockFreeBytes(set->keeper) >= required_size)
+ else if (GenerationBlockIsEmpty(KeeperBlock(set)) &&
+ GenerationBlockFreeBytes(KeeperBlock(set)) >= required_size)
{
- block = set->keeper;
+ block = KeeperBlock(set);
}
else
{
GenerationBlockFree(GenerationContext *set, GenerationBlock *block)
{
/* Make sure nobody tries to free the keeper block */
- Assert(block != set->keeper);
+ Assert(!IsKeeperBlock(set, block));
/* We shouldn't be freeing the freeblock either */
Assert(block != set->freeblock);
set = block->context;
/* Don't try to free the keeper block, just mark it empty */
- if (block == set->keeper)
+ if (IsKeeperBlock(set, block))
{
GenerationBlockMarkEmpty(block);
return;
{
MemoryContextData header; /* Standard memory-context fields */
/* Allocation parameters for this context: */
- Size chunkSize; /* the requested (non-aligned) chunk size */
- Size fullChunkSize; /* chunk size with chunk header and alignment */
- Size blockSize; /* the size to make each block of chunks */
+ uint32 chunkSize; /* the requested (non-aligned) chunk size */
+ uint32 fullChunkSize; /* chunk size with chunk header and alignment */
+ uint32 blockSize; /* the size to make each block of chunks */
int32 chunksPerBlock; /* number of chunks that fit in 1 block */
int32 curBlocklistIndex; /* index into the blocklist[] element
* containing the fullest, blocks */
* blockSize: allocation block size
* chunkSize: allocation chunk size
*
- * The MAXALIGN(chunkSize) may not exceed MEMORYCHUNK_MAX_VALUE
+ * The Slab_CHUNKHDRSZ + MAXALIGN(chunkSize + 1) may not exceed
+ * MEMORYCHUNK_MAX_VALUE.
+ * 'blockSize' may not exceed MEMORYCHUNK_MAX_BLOCKOFFSET.
*/
MemoryContext
SlabContextCreate(MemoryContext parent,
/* ensure MemoryChunk's size is properly maxaligned */
StaticAssertDecl(Slab_CHUNKHDRSZ == MAXALIGN(Slab_CHUNKHDRSZ),
"sizeof(MemoryChunk) is not maxaligned");
- Assert(MAXALIGN(chunkSize) <= MEMORYCHUNK_MAX_VALUE);
+ Assert(blockSize <= MEMORYCHUNK_MAX_BLOCKOFFSET);
/*
* Ensure there's enough space to store the pointer to the next free chunk
fullChunkSize = Slab_CHUNKHDRSZ + MAXALIGN(chunkSize);
#endif
+ Assert(fullChunkSize <= MEMORYCHUNK_MAX_VALUE);
+
/* compute the number of chunks that will fit on each block */
chunksPerBlock = (blockSize - Slab_BLOCKHDRSZ) / fullChunkSize;
*/
/* Fill in SlabContext-specific header fields */
- slab->chunkSize = chunkSize;
- slab->fullChunkSize = fullChunkSize;
- slab->blockSize = blockSize;
+ slab->chunkSize = (uint32) chunkSize;
+ slab->fullChunkSize = (uint32) fullChunkSize;
+ slab->blockSize = (uint32) blockSize;
slab->chunksPerBlock = chunksPerBlock;
slab->curBlocklistIndex = 0;
/* make sure we only allow correct request size */
if (unlikely(size != slab->chunkSize))
- elog(ERROR, "unexpected alloc chunk size %zu (expected %zu)",
+ elog(ERROR, "unexpected alloc chunk size %zu (expected %u)",
size, slab->chunkSize);
/*
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