diff --git a/src/backend/utils/mmgr/aset.c b/src/backend/utils/mmgr/aset.c
index b6eeb8abab..e6d86a54d7 100644
--- a/src/backend/utils/mmgr/aset.c
+++ b/src/backend/utils/mmgr/aset.c
@@ -674,6 +674,15 @@ AllocSetDelete(MemoryContext context)
 	free(set);
 }

+static Size pow2_size(Size size)
+{
+	Size s = 1;
+	while (s < size)
+		s *= 2;
+
+	return s;
+}
+
 /*
  * AllocSetAlloc
  *		Returns pointer to allocated memory of given size or NULL if
@@ -699,13 +708,16 @@ AllocSetAlloc(MemoryContext context, Size size)

 	AssertArg(AllocSetIsValid(set));

+	fprintf(stderr, "AllocSetAlloc %ld %ld %ld\n", size, pow2_size(size), pow2_size(size+1));
+	fflush(stderr);
+
 	/*
 	 * If requested size exceeds maximum for chunks, allocate an entire block
 	 * for this request.
 	 */
-	if (size > set->allocChunkLimit)
+	if (size + 1 > set->allocChunkLimit)
 	{
-		chunk_size = MAXALIGN(size);
+		chunk_size = MAXALIGN(size + 1);
 		blksize = chunk_size + ALLOC_BLOCKHDRSZ + ALLOC_CHUNKHDRSZ;
 		block = (AllocBlock) malloc(blksize);
 		if (block == NULL)
@@ -725,7 +737,16 @@ AllocSetAlloc(MemoryContext context, Size size)
 		chunk->requested_size = size;
 		/* set mark to catch clobber of "unused" space */
 		if (size < chunk_size)
+		{
 			set_sentinel(MemoryChunkGetPointer(chunk), size);
+			fprintf(stderr, "sentinel added\n");
+			fflush(stderr);
+		}
+		else
+		{
+			fprintf(stderr, "A sentinel not added\n");
+			fflush(stderr);
+		}
 #endif
 #ifdef RANDOMIZE_ALLOCATED_MEMORY
 		/* fill the allocated space with junk */
@@ -767,7 +788,7 @@ AllocSetAlloc(MemoryContext context, Size size)
 	 * If one is found, remove it from the free list, make it again a member
 	 * of the alloc set and return its data address.
 	 */
-	fidx = AllocSetFreeIndex(size);
+	fidx = AllocSetFreeIndex(size+1);
 	chunk = set->freelist[fidx];
 	if (chunk != NULL)
 	{
@@ -784,7 +805,16 @@ AllocSetAlloc(MemoryContext context, Size size)
 		chunk->requested_size = size;
 		/* set mark to catch clobber of "unused" space */
 		if (size < GetChunkSizeFromFreeListIdx(fidx))
+		{
 			set_sentinel(MemoryChunkGetPointer(chunk), size);
+			fprintf(stderr, "sentinel added\n");
+			fflush(stderr);
+		}
+		else
+		{
+			fprintf(stderr, "B sentinel not added\n");
+			fflush(stderr);
+		}
 #endif
 #ifdef RANDOMIZE_ALLOCATED_MEMORY
 		/* fill the allocated space with junk */
@@ -950,7 +980,16 @@ AllocSetAlloc(MemoryContext context, Size size)
 	chunk->requested_size = size;
 	/* set mark to catch clobber of "unused" space */
 	if (size < chunk_size)
+	{
 		set_sentinel(MemoryChunkGetPointer(chunk), size);
+		fprintf(stderr, "sentinel added\n");
+		fflush(stderr);
+	}
+	else
+	{
+		fprintf(stderr, "C sentinel not added\n");
+		fflush(stderr);
+	}
 #endif
 #ifdef RANDOMIZE_ALLOCATED_MEMORY
 	/* fill the allocated space with junk */
@@ -994,7 +1033,7 @@ AllocSetFree(void *pointer)
 			/* Test for someone scribbling on unused space in chunk */
 			if (chunk->requested_size < chunk_size)
 				if (!sentinel_ok(pointer, chunk->requested_size))
-					elog(WARNING, "detected write past chunk end in %s %p",
+					elog(ERROR, "detected write past chunk end in %s %p",
 						 set->header.name, chunk);
 		}
 #endif
@@ -1034,7 +1073,7 @@ AllocSetFree(void *pointer)
 		/* Test for someone scribbling on unused space in chunk */
 		if (chunk->requested_size < GetChunkSizeFromFreeListIdx(fidx))
 			if (!sentinel_ok(pointer, chunk->requested_size))
-				elog(WARNING, "detected write past chunk end in %s %p",
+				elog(ERROR, "detected write past chunk end in %s %p",
 					 set->header.name, chunk);
 #endif

@@ -1078,6 +1117,9 @@ AllocSetRealloc(void *pointer, Size size)
 	MemoryChunk *chunk = PointerGetMemoryChunk(pointer);
 	Size		oldsize;

+	fprintf(stderr, "AllocSetRelloc %ld %ld %ld\n", size, pow2_size(size), pow2_size(size+1));
+	fflush(stderr);
+
 	/* Allow access to private part of chunk header. */
 	VALGRIND_MAKE_MEM_DEFINED(chunk, ALLOCCHUNK_PRIVATE_LEN);

@@ -1100,7 +1142,7 @@ AllocSetRealloc(void *pointer, Size size)
 		/* Test for someone scribbling on unused space in chunk */
 		if (chunk->requested_size < oldsize)
 			if (!sentinel_ok(pointer, chunk->requested_size))
-				elog(WARNING, "detected write past chunk end in %s %p",
+				elog(ERROR, "detected write past chunk end in %s %p",
 					 set->header.name, chunk);
 #endif

@@ -1111,7 +1153,7 @@ AllocSetRealloc(void *pointer, Size size)
 		if (block->freeptr != block->endptr)
 			elog(ERROR, "could not find block containing chunk %p", chunk);

-		chksize = MAXALIGN(size);
+		chksize = MAXALIGN(size+1);

 		/* Do the realloc */
 		blksize = chksize + ALLOC_BLOCKHDRSZ + ALLOC_CHUNKHDRSZ;
@@ -1163,7 +1205,16 @@ AllocSetRealloc(void *pointer, Size size)
 		chunk->requested_size = size;
 		/* set mark to catch clobber of "unused" space */
 		if (size < chksize)
+		{
 			set_sentinel(pointer, size);
+			fprintf(stderr, "sentinel added\n");
+			fflush(stderr);
+		}
+		else
+		{
+			fprintf(stderr, "D sentinel not added\n");
+			fflush(stderr);
+		}
 #else							/* !MEMORY_CONTEXT_CHECKING */

 		/*
@@ -1191,7 +1242,7 @@ AllocSetRealloc(void *pointer, Size size)
 	/* Test for someone scribbling on unused space in chunk */
 	if (chunk->requested_size < oldsize)
 		if (!sentinel_ok(pointer, chunk->requested_size))
-			elog(WARNING, "detected write past chunk end in %s %p",
+			elog(ERROR, "detected write past chunk end in %s %p",
 				 set->header.name, chunk);
 #endif

@@ -1200,7 +1251,7 @@ AllocSetRealloc(void *pointer, Size size)
 	 * allocated area already is >= the new size.  (In particular, we will
 	 * fall out here if the requested size is a decrease.)
 	 */
-	if (oldsize >= size)
+	if (oldsize >= size + 1)
 	{
 #ifdef MEMORY_CONTEXT_CHECKING
 		Size		oldrequest = chunk->requested_size;
@@ -1227,7 +1278,17 @@ AllocSetRealloc(void *pointer, Size size)

 		/* set mark to catch clobber of "unused" space */
 		if (size < oldsize)
+		{
 			set_sentinel(pointer, size);
+
+			fprintf(stderr, "sentinel added\n");
+			fflush(stderr);
+		}
+		else
+		{
+			fprintf(stderr, "E sentinel not added\n");
+			fflush(stderr);
+		}
 #else							/* !MEMORY_CONTEXT_CHECKING */

 		/*
@@ -1532,7 +1593,7 @@ AllocSetCheck(MemoryContext context)
 			 */
 			if (dsize != InvalidAllocSize && dsize < chsize &&
 				!sentinel_ok(chunk, ALLOC_CHUNKHDRSZ + dsize))
-				elog(WARNING, "problem in alloc set %s: detected write past chunk end in block %p, chunk %p",
+				elog(ERROR, "problem in alloc set %s: detected write past chunk end in block %p, chunk %p",
 					 name, block, chunk);

 			/*
diff --git a/src/backend/utils/mmgr/generation.c b/src/backend/utils/mmgr/generation.c
index b39894ec94..2f1363967d 100644
--- a/src/backend/utils/mmgr/generation.c
+++ b/src/backend/utils/mmgr/generation.c
@@ -323,6 +323,15 @@ GenerationDelete(MemoryContext context)
 	free(context);
 }

+static Size pow2_size(Size size)
+{
+	Size s = 1;
+	while (s < size)
+		s *= 2;
+
+	return s;
+}
+
 /*
  * GenerationAlloc
  *		Returns pointer to allocated memory of given size or NULL if
@@ -345,6 +354,9 @@ GenerationAlloc(MemoryContext context, Size size)
 	Size		chunk_size = MAXALIGN(size);
 	Size		required_size = chunk_size + Generation_CHUNKHDRSZ;

+	fprintf(stderr, "GenerationAlloc %ld %ld %ld\n", size, pow2_size(size), pow2_size(size+1));
+	fflush(stderr);
+
 	/* is it an over-sized chunk? if yes, allocate special block */
 	if (chunk_size > set->allocChunkLimit)
 	{
@@ -709,6 +721,9 @@ GenerationRealloc(void *pointer, Size size)
 	GenerationPointer newPointer;
 	Size		oldsize;

+	fprintf(stderr, "GenerationRealloc %ld %ld %ld\n", size, pow2_size(size), pow2_size(size+1));
+	fflush(stderr);
+
 	/* Allow access to private part of chunk header. */
 	VALGRIND_MAKE_MEM_DEFINED(chunk, GENERATIONCHUNK_PRIVATE_LEN);