Fix lg_chunk clamping for config_cache_oblivious.

Fix lg_chunk clamping to take into account cache-oblivious large
allocation.  This regression only resulted in incorrect behavior if
!config_fill (false unless --disable-fill specified) and
config_cache_oblivious (true unless --disable-cache-oblivious
specified).

This regression was introduced by
8a03cf0 (Implement cache index
randomization for large allocations.), which was first released in
4.0.0.

This resolves jemalloc#555.

Author: jasone

src/arena.c

@@ -2710,6 +2710,7 @@ arena_malloc_hard(tsdn_t *tsdn, arena_t *arena, size_t size, szind_t ind,
 		return (arena_malloc_small(tsdn, arena, ind, zero));
 	if (likely(size <= large_maxclass))
 		return (arena_malloc_large(tsdn, arena, ind, zero));
+	assert(index2size(ind) >= chunksize);
 	return (huge_malloc(tsdn, arena, index2size(ind), zero));
 }
 
@@ -3806,15 +3807,8 @@ arena_boot(void)
 	arena_maxrun = chunksize - (map_bias << LG_PAGE);
 	assert(arena_maxrun > 0);
 	large_maxclass = index2size(size2index(chunksize)-1);
-	if (large_maxclass > arena_maxrun) {
-		/*
-		 * For small chunk sizes it's possible for there to be fewer
-		 * non-header pages available than are necessary to serve the
-		 * size classes just below chunksize.
-		 */
-		large_maxclass = arena_maxrun;
-	}
 	assert(large_maxclass > 0);
+	assert(large_maxclass + large_pad <= arena_maxrun);
 	nlclasses = size2index(large_maxclass) - size2index(SMALL_MAXCLASS);
 	nhclasses = NSIZES - nlclasses - NBINS;
 

src/jemalloc.c

@@ -1136,16 +1136,18 @@ malloc_conf_init(void)
 
 			CONF_HANDLE_BOOL(opt_abort, "abort", true)
 			/*
-			 * Chunks always require at least one header page,
-			 * as many as 2^(LG_SIZE_CLASS_GROUP+1) data pages, and
-			 * possibly an additional page in the presence of
-			 * redzones.  In order to simplify options processing,
-			 * use a conservative bound that accommodates all these
-			 * constraints.
+			 * Chunks always require at least one header page, as
+			 * many as 2^(LG_SIZE_CLASS_GROUP+1) data pages (plus an
+			 * additional page in the presence of cache-oblivious
+			 * large), and possibly an additional page in the
+			 * presence of redzones.  In order to simplify options
+			 * processing, use a conservative bound that
+			 * accommodates all these constraints.
 			 */
 			CONF_HANDLE_SIZE_T(opt_lg_chunk, "lg_chunk", LG_PAGE +
-			    LG_SIZE_CLASS_GROUP + (config_fill ? 2 : 1),
-			    (sizeof(size_t) << 3) - 1, yes, yes, true)
+			    LG_SIZE_CLASS_GROUP + 1 + (config_cache_oblivious ||
+			    config_fill ?  1 : 0), (sizeof(size_t) << 3) - 1,
+			    yes, yes, true)
 			if (strncmp("dss", k, klen) == 0) {
 				int i;
 				bool match = false;