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Specialize MemoryContextMemAllocated().

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An AllocSet doubles the size of allocated blocks (up to maxBlockSize),
which means that the current block can represent half of the total
allocated space for the memory context. But the free space in the
current block may never have been touched, so don't count the
untouched memory as allocated for the purposes of
MemoryContextMemAllocated().

Discussion: https://postgr.es/m/ec63d70b668818255486a83ffadc3aec492c1f57.camel@j-davis.com
This commit is contained in:
Jeff Davis
2020-03-18 15:39:14 -07:00
parent 487e9861d0
commit e00912e11a
5 changed files with 77 additions and 28 deletions
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29
src/backend/utils/mmgr/slab.c
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@@ -67,6 +67,7 @@ typedef struct SlabContext
Size fullChunkSize; /* chunk size including header and alignment */
Size blockSize; /* block size */
Size headerSize; /* allocated size of context header */
Size memAllocated; /* track memory allocated for this context */
int chunksPerBlock; /* number of chunks per block */
int minFreeChunks; /* min number of free chunks in any block */
int nblocks; /* number of blocks allocated */
@@ -132,6 +133,7 @@ static void *SlabRealloc(MemoryContext context, void *pointer, Size size);
static void SlabReset(MemoryContext context);
static void SlabDelete(MemoryContext context);
static Size SlabGetChunkSpace(MemoryContext context, void *pointer);
static Size SlabMemAllocated(MemoryContext context);
static bool SlabIsEmpty(MemoryContext context);
static void SlabStats(MemoryContext context,
MemoryStatsPrintFunc printfunc, void *passthru,
@@ -150,6 +152,7 @@ static const MemoryContextMethods SlabMethods = {
SlabReset,
SlabDelete,
SlabGetChunkSpace,
SlabMemAllocated,
SlabIsEmpty,
SlabStats
#ifdef MEMORY_CONTEXT_CHECKING
@@ -262,6 +265,7 @@ SlabContextCreate(MemoryContext parent,
slab->fullChunkSize = fullChunkSize;
slab->blockSize = blockSize;
slab->headerSize = headerSize;
slab->memAllocated = 0;
slab->chunksPerBlock = chunksPerBlock;
slab->minFreeChunks = 0;
slab->nblocks = 0;
@@ -286,6 +290,17 @@ SlabContextCreate(MemoryContext parent,
return (MemoryContext) slab;
}
/*
* All memory currently allocated for this context (including fragmentation
* and freed chunks).
*/
static Size
SlabMemAllocated(MemoryContext context)
{
SlabContext *slab = (SlabContext *) context;
return slab->memAllocated;
}
/*
* SlabReset
* Frees all memory which is allocated in the given set.
@@ -322,14 +337,14 @@ SlabReset(MemoryContext context)
#endif
free(block);
slab->nblocks--;
context->mem_allocated -= slab->blockSize;
slab->memAllocated -= slab->blockSize;
}
}
slab->minFreeChunks = 0;
Assert(slab->nblocks == 0);
Assert(context->mem_allocated == 0);
Assert(slab->memAllocated == 0);
}
/*
@@ -407,7 +422,7 @@ SlabAlloc(MemoryContext context, Size size)
slab->minFreeChunks = slab->chunksPerBlock;
slab->nblocks += 1;
context->mem_allocated += slab->blockSize;
slab->memAllocated += slab->blockSize;
}
/* grab the block from the freelist (even the new block is there) */
@@ -501,7 +516,7 @@ SlabAlloc(MemoryContext context, Size size)
SlabAllocInfo(slab, chunk);
Assert(slab->nblocks * slab->blockSize == context->mem_allocated);
Assert(slab->nblocks * slab->blockSize == slab->memAllocated);
return SlabChunkGetPointer(chunk);
}
@@ -578,13 +593,13 @@ SlabFree(MemoryContext context, void *pointer)
{
free(block);
slab->nblocks--;
context->mem_allocated -= slab->blockSize;
slab->memAllocated -= slab->blockSize;
}
else
dlist_push_head(&slab->freelist[block->nfree], &block->node);
Assert(slab->nblocks >= 0);
Assert(slab->nblocks * slab->blockSize == context->mem_allocated);
Assert(slab->nblocks * slab->blockSize == slab->memAllocated);
}
/*
@@ -804,7 +819,7 @@ SlabCheck(MemoryContext context)
}
}
Assert(slab->nblocks * slab->blockSize == context->mem_allocated);
Assert(slab->nblocks * slab->blockSize == slab->memAllocated);
}
#endif /* MEMORY_CONTEXT_CHECKING */