Attached is a patch that explicitly tracks allocated memory (the blocks,
not the chunks) for each memory context, as well as its children.
This is a prerequisite for memory-bounded HashAgg, which I intend to
submit for the next CF. Hashjoin tracks the tuple sizes that it adds to
the hash table, which is a good estimate for Hashjoin. But I don't think
it's as easy for Hashagg, for which we need to track transition values,
etc. (also, for HashAgg, I expect that the overhead will be more
significant than for Hashjoin). If we track the space used by the memory
contexts directly, it's easier and more accurate.
I did some simple pgbench select-only tests, and I didn't see any TPS
difference.
Regards,
Jeff Davis
*** a/src/backend/utils/mmgr/aset.c
--- b/src/backend/utils/mmgr/aset.c
***************
*** 242,247 **** typedef struct AllocChunkData
--- 242,249 ----
#define AllocChunkGetPointer(chk) \
((AllocPointer)(((char *)(chk)) + ALLOC_CHUNKHDRSZ))
+ static void update_allocation(MemoryContext context, int64 size);
+
/*
* These functions implement the MemoryContext API for AllocSet contexts.
*/
***************
*** 500,505 **** AllocSetContextCreate(MemoryContext parent,
--- 502,510 ----
errdetail("Failed while creating memory context \"%s\".",
name)));
}
+
+ update_allocation((MemoryContext) context, blksize);
+
block->aset = context;
block->freeptr = ((char *) block) + ALLOC_BLOCKHDRSZ;
block->endptr = ((char *) block) + blksize;
***************
*** 590,595 **** AllocSetReset(MemoryContext context)
--- 595,601 ----
else
{
/* Normal case, release the block */
+ update_allocation(context, -(block->endptr - ((char*) block)));
#ifdef CLOBBER_FREED_MEMORY
wipe_mem(block, block->freeptr - ((char *) block));
#endif
***************
*** 632,637 **** AllocSetDelete(MemoryContext context)
--- 638,644 ----
{
AllocBlock next = block->next;
+ update_allocation(context, -(block->endptr - ((char*) block)));
#ifdef CLOBBER_FREED_MEMORY
wipe_mem(block, block->freeptr - ((char *) block));
#endif
***************
*** 678,683 **** AllocSetAlloc(MemoryContext context, Size size)
--- 685,693 ----
errmsg("out of memory"),
errdetail("Failed on request of size %zu.", size)));
}
+
+ update_allocation(context, blksize);
+
block->aset = set;
block->freeptr = block->endptr = ((char *) block) + blksize;
***************
*** 873,878 **** AllocSetAlloc(MemoryContext context, Size size)
--- 883,890 ----
errdetail("Failed on request of size %zu.", size)));
}
+ update_allocation(context, blksize);
+
block->aset = set;
block->freeptr = ((char *) block) + ALLOC_BLOCKHDRSZ;
block->endptr = ((char *) block) + blksize;
***************
*** 976,981 **** AllocSetFree(MemoryContext context, void *pointer)
--- 988,994 ----
set->blocks = block->next;
else
prevblock->next = block->next;
+ update_allocation(context, -(block->endptr - ((char*) block)));
#ifdef CLOBBER_FREED_MEMORY
wipe_mem(block, block->freeptr - ((char *) block));
#endif
***************
*** 1088,1093 **** AllocSetRealloc(MemoryContext context, void *pointer, Size size)
--- 1101,1107 ----
AllocBlock prevblock = NULL;
Size chksize;
Size blksize;
+ Size oldblksize;
while (block != NULL)
{
***************
*** 1105,1110 **** AllocSetRealloc(MemoryContext context, void *pointer, Size size)
--- 1119,1126 ----
/* 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)
{
***************
*** 1114,1119 **** AllocSetRealloc(MemoryContext context, void *pointer, Size size)
--- 1130,1136 ----
errmsg("out of memory"),
errdetail("Failed on request of size %zu.", size)));
}
+ update_allocation(context, blksize - oldblksize);
block->freeptr = block->endptr = ((char *) block) + blksize;
/* Update pointers since block has likely been moved */
***************
*** 1277,1282 **** AllocSetStats(MemoryContext context, int level)
--- 1294,1320 ----
}
+ /*
+ * update_allocation
+ *
+ * Track newly-allocated or newly-freed memory (freed memory should be
+ * negative).
+ */
+ static void
+ update_allocation(MemoryContext context, int64 size)
+ {
+ MemoryContext parent;
+
+ context->self_allocated += size;
+
+ for (parent = context; parent != NULL; parent = parent->parent)
+ {
+ parent->total_allocated += size;
+ Assert(parent->self_allocated >= 0);
+ Assert(parent->total_allocated >= 0);
+ }
+ }
+
#ifdef MEMORY_CONTEXT_CHECKING
/*
*** a/src/backend/utils/mmgr/mcxt.c
--- b/src/backend/utils/mmgr/mcxt.c
***************
*** 324,329 **** MemoryContextAllowInCriticalSection(MemoryContext context, bool allow)
--- 324,344 ----
}
/*
+ * MemoryContextGetAllocated
+ *
+ * Return memory allocated by the system to this context. If total is true,
+ * include child contexts.
+ */
+ int64
+ MemoryContextGetAllocated(MemoryContext context, bool total)
+ {
+ if (total)
+ return context->total_allocated;
+ else
+ return context->self_allocated;
+ }
+
+ /*
* GetMemoryChunkSpace
* Given a currently-allocated chunk, determine the total space
* it occupies (including all memory-allocation overhead).
***************
*** 576,581 **** MemoryContextCreate(NodeTag tag, Size size,
--- 591,598 ----
node->firstchild = NULL;
node->nextchild = NULL;
node->isReset = true;
+ node->total_allocated = 0;
+ node->self_allocated = 0;
node->name = ((char *) node) + size;
strcpy(node->name, name);
*** a/src/include/nodes/memnodes.h
--- b/src/include/nodes/memnodes.h
***************
*** 60,65 **** typedef struct MemoryContextData
--- 60,67 ----
MemoryContext nextchild; /* next child of same parent */
char *name; /* context name (just for debugging) */
bool isReset; /* T = no space alloced since last reset */
+ int64 total_allocated; /* including child contexts */
+ int64 self_allocated; /* not including child contexts */
#ifdef USE_ASSERT_CHECKING
bool allowInCritSection; /* allow palloc in critical section */
#endif
*** a/src/include/utils/memutils.h
--- b/src/include/utils/memutils.h
***************
*** 96,101 **** extern void MemoryContextDeleteChildren(MemoryContext context);
--- 96,102 ----
extern void MemoryContextResetAndDeleteChildren(MemoryContext context);
extern void MemoryContextSetParent(MemoryContext context,
MemoryContext new_parent);
+ extern int64 MemoryContextGetAllocated(MemoryContext context, bool total);
extern Size GetMemoryChunkSpace(void *pointer);
extern MemoryContext GetMemoryChunkContext(void *pointer);
extern MemoryContext MemoryContextGetParent(MemoryContext context);
--
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