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Add transparent block-level memory accounting

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Adds accounting of memory allocated in a memory context. Compared to
various ad hoc solutions, the main advantage is that the accounting is
transparent and does not require direct control over allocations (this
matters for use cases where the allocations happen in user code, like
for example aggregate states allocated in a transition functions).

To reduce overhead, the accounting happens at the block level (not for
individual chunks) and only the context immediately owning the block is
updated. When inquiring about amount of memory allocated in a context,
we have to recursively walk all children contexts.

This "lazy" accounting works well for cases with relatively small number
of contexts in the relevant subtree and/or with infrequent inquiries.

Author: Jeff Davis
Reivewed-by: Tomas Vondra, Melanie Plageman, Soumyadeep Chakraborty
Discussion: https://www.postgresql.org/message-id/flat/027a129b8525601c6a680d27ce3a7172dab61aab.camel@j-davis.com
This commit is contained in:
Tomas Vondra
2019-10-01 03:13:39 +02:00
parent 36d22dd95b
commit 5dd7fc1519
7 changed files with 121 additions and 0 deletions
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38
src/backend/utils/mmgr/aset.c
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@@ -458,6 +458,9 @@ AllocSetContextCreateInternal(MemoryContext parent,
parent,
name);
((MemoryContext) set)->mem_allocated =
set->keeper->endptr - ((char *) set);
return (MemoryContext) set;
}
}
@@ -546,6 +549,8 @@ AllocSetContextCreateInternal(MemoryContext parent,
parent,
name);
((MemoryContext) set)->mem_allocated = firstBlockSize;
return (MemoryContext) set;
}
@@ -566,6 +571,7 @@ AllocSetReset(MemoryContext context)
{
AllocSet set = (AllocSet) context;
AllocBlock block;
Size keepersize = set->keeper->endptr - ((char *) set);
AssertArg(AllocSetIsValid(set));
@@ -604,6 +610,8 @@ AllocSetReset(MemoryContext context)
else
{
/* Normal case, release the block */
context->mem_allocated -= block->endptr - ((char*) block);
#ifdef CLOBBER_FREED_MEMORY
wipe_mem(block, block->freeptr - ((char *) block));
#endif
@@ -612,6 +620,8 @@ AllocSetReset(MemoryContext context)
block = next;
}
Assert(context->mem_allocated == keepersize);
/* Reset block size allocation sequence, too */
set->nextBlockSize = set->initBlockSize;
}
@@ -628,6 +638,7 @@ AllocSetDelete(MemoryContext context)
{
AllocSet set = (AllocSet) context;
AllocBlock block = set->blocks;
Size keepersize = set->keeper->endptr - ((char *) set);
AssertArg(AllocSetIsValid(set));
@@ -683,6 +694,9 @@ AllocSetDelete(MemoryContext context)
{
AllocBlock next = block->next;
if (block != set->keeper)
context->mem_allocated -= block->endptr - ((char *) block);
#ifdef CLOBBER_FREED_MEMORY
wipe_mem(block, block->freeptr - ((char *) block));
#endif
@@ -693,6 +707,8 @@ AllocSetDelete(MemoryContext context)
block = next;
}
Assert(context->mem_allocated == keepersize);
/* Finally, free the context header, including the keeper block */
free(set);
}
@@ -733,6 +749,9 @@ AllocSetAlloc(MemoryContext context, Size size)
block = (AllocBlock) malloc(blksize);
if (block == NULL)
return NULL;
context->mem_allocated += blksize;
block->aset = set;
block->freeptr = block->endptr = ((char *) block) + blksize;
@@ -928,6 +947,8 @@ AllocSetAlloc(MemoryContext context, Size size)
if (block == NULL)
return NULL;
context->mem_allocated += blksize;
block->aset = set;
block->freeptr = ((char *) block) + ALLOC_BLOCKHDRSZ;
block->endptr = ((char *) block) + blksize;
@@ -1028,6 +1049,9 @@ AllocSetFree(MemoryContext context, void *pointer)
set->blocks = block->next;
if (block->next)
block->next->prev = block->prev;
context->mem_allocated -= block->endptr - ((char*) block);
#ifdef CLOBBER_FREED_MEMORY
wipe_mem(block, block->freeptr - ((char *) block));
#endif
@@ -1144,6 +1168,7 @@ AllocSetRealloc(MemoryContext context, void *pointer, Size size)
AllocBlock block = (AllocBlock) (((char *) chunk) - ALLOC_BLOCKHDRSZ);
Size chksize;
Size blksize;
Size oldblksize;
/*
* Try to verify that we have a sane block pointer: it should
@@ -1159,6 +1184,8 @@ AllocSetRealloc(MemoryContext context, void *pointer, Size size)
/* Do the realloc */
chksize = MAXALIGN(size);
blksize = chksize + ALLOC_BLOCKHDRSZ + ALLOC_CHUNKHDRSZ;
oldblksize = block->endptr - ((char *)block);
block = (AllocBlock) realloc(block, blksize);
if (block == NULL)
{
@@ -1166,6 +1193,9 @@ AllocSetRealloc(MemoryContext context, void *pointer, Size size)
VALGRIND_MAKE_MEM_NOACCESS(chunk, ALLOCCHUNK_PRIVATE_LEN);
return NULL;
}
context->mem_allocated += blksize - oldblksize;
block->freeptr = block->endptr = ((char *) block) + blksize;
/* Update pointers since block has likely been moved */
@@ -1383,6 +1413,7 @@ AllocSetCheck(MemoryContext context)
const char *name = set->header.name;
AllocBlock prevblock;
AllocBlock block;
int64 total_allocated = 0;
for (prevblock = NULL, block = set->blocks;
block != NULL;
@@ -1393,6 +1424,11 @@ AllocSetCheck(MemoryContext context)
long blk_data = 0;
long nchunks = 0;
if (set->keeper == block)
total_allocated += block->endptr - ((char *) set);
else
total_allocated += block->endptr - ((char *) block);
/*
* Empty block - empty can be keeper-block only
*/
@@ -1479,6 +1515,8 @@ AllocSetCheck(MemoryContext context)
elog(WARNING, "problem in alloc set %s: found inconsistent memory block %p",
name, block);
}
Assert(total_allocated == context->mem_allocated);
}
#endif /* MEMORY_CONTEXT_CHECKING */