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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