diff --git a/include/jemalloc/internal/arena.h b/include/jemalloc/internal/arena.h
index 42086ca1..50b296e4 100644
--- a/include/jemalloc/internal/arena.h
+++ b/include/jemalloc/internal/arena.h
@@ -312,7 +312,7 @@ struct arena_s {
 
 	/*
 	 * Size/address-ordered tree of this arena's available runs.  The tree
-	 * is used for first-best-fit run allocation.
+	 * is used for first-fit run allocation.
 	 */
 	arena_avail_tree_t	runs_avail;
 
diff --git a/src/arena.c b/src/arena.c
index 34329a62..6f4197b2 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -907,23 +907,55 @@ arena_chunk_ralloc_huge_expand(arena_t *arena, void *chunk, size_t oldsize,
 	return (err);
 }
 
+/* Do first-fit run selection. */
+static arena_run_t *
+arena_run_first_fit(arena_t *arena, size_t size)
+{
+	arena_run_t *run;
+	index_t index, max_index;
+
+	assert(size == s2u(size));
+	assert(size == PAGE_CEILING(size));
+
+	/*
+	 * Iterate over all size classes that are at least large enough to
+	 * satisfy the request, search for the lowest run of each size class,
+	 * and choose the lowest of the runs found.
+	 */
+	run = NULL;
+	for (index = size2index(size), max_index = size2index(arena_maxclass);
+	    index <= max_index;) {
+		arena_run_t *currun;
+		arena_chunk_t *currun_chunk;
+		size_t currun_pageind, currun_size;
+		size_t usize = PAGE_CEILING(index2size(index));
+		arena_chunk_map_misc_t *key = (arena_chunk_map_misc_t *)(usize |
+		    CHUNK_MAP_KEY);
+		arena_chunk_map_misc_t *miscelm =
+		    arena_avail_tree_nsearch(&arena->runs_avail, key);
+		if (miscelm == NULL)
+			break;
+		currun = &miscelm->run;
+		if (run == NULL || (uintptr_t)currun < (uintptr_t)run)
+			run = currun;
+		currun_chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(currun);
+		currun_pageind = arena_miscelm_to_pageind(miscelm);
+		currun_size = arena_mapbits_unallocated_size_get(currun_chunk,
+		    currun_pageind);
+		assert(size2index(currun_size) + 1 > index);
+		index = size2index(currun_size) + 1;
+	}
+
+	return (run);
+}
+
 static arena_run_t *
 arena_run_alloc_large_helper(arena_t *arena, size_t size, bool zero)
 {
-	arena_chunk_map_misc_t *miscelm;
-	arena_chunk_map_misc_t *key;
-	size_t usize;
-
-	usize = s2u(size);
-	key = (arena_chunk_map_misc_t *)(usize | CHUNK_MAP_KEY);
-	miscelm = arena_avail_tree_nsearch(&arena->runs_avail, key);
-	if (miscelm != NULL) {
-		arena_run_t *run = &miscelm->run;
-		arena_run_split_large(arena, &miscelm->run, size, zero);
-		return (run);
-	}
-
-	return (NULL);
+	arena_run_t *run = arena_run_first_fit(arena, s2u(size));
+	if (run != NULL)
+		arena_run_split_large(arena, run, size, zero);
+	return (run);
 }
 
 static arena_run_t *
@@ -961,20 +993,10 @@ arena_run_alloc_large(arena_t *arena, size_t size, bool zero)
 static arena_run_t *
 arena_run_alloc_small_helper(arena_t *arena, size_t size, index_t binind)
 {
-	arena_run_t *run;
-	arena_chunk_map_misc_t *miscelm;
-	arena_chunk_map_misc_t *key;
-
-	assert(size == s2u(size));
-	key = (arena_chunk_map_misc_t *)(PAGE_CEILING(size) | CHUNK_MAP_KEY);
-	miscelm = arena_avail_tree_nsearch(&arena->runs_avail, key);
-	if (miscelm != NULL) {
-		run = &miscelm->run;
+	arena_run_t *run = arena_run_first_fit(arena, PAGE_CEILING(size));
+	if (run != NULL)
 		arena_run_split_small(arena, run, size, binind);
-		return (run);
-	}
-
-	return (NULL);
+	return (run);
 }
 
 static arena_run_t *
diff --git a/src/chunk.c b/src/chunk.c
index 972fecde..875fa4cc 100644
--- a/src/chunk.c
+++ b/src/chunk.c
@@ -62,6 +62,39 @@ chunk_deregister(const void *chunk, const extent_node_t *node)
 	}
 }
 
+/* Do first-fit chunk selection. */
+static extent_node_t *
+chunk_first_fit(arena_t *arena, extent_tree_t *chunks_szad, size_t size)
+{
+	extent_node_t *node;
+	index_t index;
+
+	assert(size == CHUNK_CEILING(size));
+
+	/*
+	 * Iterate over all size classes that are at least large enough to
+	 * satisfy the request, search for the lowest chunk of each size class,
+	 * and choose the lowest of the chunks found.
+	 */
+	node = NULL;
+	for (index = size2index(size); index < NSIZES;) {
+		extent_node_t *curnode;
+		extent_node_t key;
+		extent_node_init(&key, arena, NULL,
+		    CHUNK_CEILING(index2size(index)), false);
+		curnode = extent_tree_szad_nsearch(chunks_szad, &key);
+		if (curnode == NULL)
+			break;
+		if (node == NULL || (uintptr_t)extent_node_addr_get(curnode) <
+		    (uintptr_t)extent_node_addr_get(node))
+			node = curnode;
+		assert(size2index(extent_node_size_get(curnode)) + 1 > index);
+		index = size2index(extent_node_size_get(curnode)) + 1;
+	}
+
+	return (node);
+}
+
 static void *
 chunk_recycle(arena_t *arena, extent_tree_t *chunks_szad,
     extent_tree_t *chunks_ad, bool cache, void *new_addr, size_t size,
@@ -69,7 +102,6 @@ chunk_recycle(arena_t *arena, extent_tree_t *chunks_szad,
 {
 	void *ret;
 	extent_node_t *node;
-	extent_node_t key;
 	size_t alloc_size, leadsize, trailsize;
 	bool zeroed;
 
@@ -80,10 +112,13 @@ chunk_recycle(arena_t *arena, extent_tree_t *chunks_szad,
 	/* Beware size_t wrap-around. */
 	if (alloc_size < size)
 		return (NULL);
-	extent_node_init(&key, arena, new_addr, alloc_size, false);
 	malloc_mutex_lock(&arena->chunks_mtx);
-	node = (new_addr != NULL) ? extent_tree_ad_search(chunks_ad, &key) :
-	    extent_tree_szad_nsearch(chunks_szad, &key);
+	if (new_addr != NULL || size == chunksize) {
+		extent_node_t key;
+		extent_node_init(&key, arena, new_addr, alloc_size, false);
+		node = extent_tree_ad_search(chunks_ad, &key);
+	} else
+		node = chunk_first_fit(arena, chunks_szad, alloc_size);
 	if (node == NULL || (new_addr != NULL && extent_node_size_get(node) <
 	    size)) {
 		malloc_mutex_unlock(&arena->chunks_mtx);