Fix two valgrind issues in slab allocator.

anarazel · anarazel · commit 490e9a98ff96 · 2017-04-04T14:26:42.000-07:00
During allocation VALGRIND_MAKE_MEM_DEFINED was called with a pointer as size. That kind of works, but makes valgrind exceedingly slow for workloads involving the slab allocator. Secondly there was an access to memory marked as unreachable within SlabCheck(). Fix that too. Author: Tomas Vondra Discussion: https://postgr.es/m/a6543b6d-6015-99b1-63ef-3ed55a76a730@2ndquadrant.com
diff --git a/src/backend/utils/mmgr/slab.c b/src/backend/utils/mmgr/slab.c
@@ -403,7 +403,7 @@ SlabAlloc(MemoryContext context, Size size)
 	 * Remove the chunk from the freelist head. The index of the next free
 	 * chunk is stored in the chunk itself.
 	 */
-	VALGRIND_MAKE_MEM_DEFINED(chunk, SlabChunkGetPointer(chunk));
+	VALGRIND_MAKE_MEM_DEFINED(SlabChunkGetPointer(chunk), sizeof(int32));
 	block->firstFreeChunk = *(int32 *) SlabChunkGetPointer(chunk);
 
 	Assert(block->firstFreeChunk >= 0);
@@ -725,6 +725,7 @@ SlabCheck(MemoryContext context)
 
 				/* read index of the next free chunk */
 				chunk = SlabBlockGetChunk(slab, block, idx);
+				VALGRIND_MAKE_MEM_DEFINED(SlabChunkGetPointer(chunk), sizeof(int32));
 				idx = *(int32 *) SlabChunkGetPointer(chunk);
 			}
 
