diff --git a/Makefile.in b/Makefile.in
index a4555c03..f60823f5 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -159,6 +159,7 @@ TESTS_UNIT := $(srcroot)test/unit/atomic.c \
 	$(srcroot)test/unit/quarantine.c \
 	$(srcroot)test/unit/rb.c \
 	$(srcroot)test/unit/rtree.c \
+	$(srcroot)test/unit/run_quantize.c \
 	$(srcroot)test/unit/SFMT.c \
 	$(srcroot)test/unit/size_classes.c \
 	$(srcroot)test/unit/smoothstep.c \
diff --git a/include/jemalloc/internal/arena.h b/include/jemalloc/internal/arena.h
index 561b5886..f98aeb80 100644
--- a/include/jemalloc/internal/arena.h
+++ b/include/jemalloc/internal/arena.h
@@ -494,9 +494,15 @@ extern size_t		map_bias; /* Number of arena chunk header pages. */
 extern size_t		map_misc_offset;
 extern size_t		arena_maxrun; /* Max run size for arenas. */
 extern size_t		large_maxclass; /* Max large size class. */
+extern size_t		small_maxrun; /* Max run size for small size classes. */
 extern unsigned		nlclasses; /* Number of large size classes. */
 extern unsigned		nhclasses; /* Number of huge size classes. */
 
+#ifdef JEMALLOC_JET
+typedef size_t (run_quantize_t)(size_t);
+extern run_quantize_t *run_quantize_floor;
+extern run_quantize_t *run_quantize_ceil;
+#endif
 void	arena_chunk_cache_maybe_insert(arena_t *arena, extent_node_t *node,
     bool cache);
 void	arena_chunk_cache_maybe_remove(arena_t *arena, extent_node_t *node,
diff --git a/include/jemalloc/internal/private_symbols.txt b/include/jemalloc/internal/private_symbols.txt
index c12baadb..3e37a61a 100644
--- a/include/jemalloc/internal/private_symbols.txt
+++ b/include/jemalloc/internal/private_symbols.txt
@@ -445,6 +445,8 @@ rtree_subtree_read_hard
 rtree_subtree_tryread
 rtree_val_read
 rtree_val_write
+run_quantize_ceil
+run_quantize_floor
 s2u
 s2u_compute
 s2u_lookup
diff --git a/src/arena.c b/src/arena.c
index 77c691a1..ff5b5fb8 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -21,7 +21,7 @@ size_t		map_bias;
 size_t		map_misc_offset;
 size_t		arena_maxrun; /* Max run size for arenas. */
 size_t		large_maxclass; /* Max large size class. */
-static size_t	small_maxrun; /* Max run size used for small size classes. */
+size_t		small_maxrun; /* Max run size for small size classes. */
 static bool	*small_run_tab; /* Valid small run page multiples. */
 unsigned	nlclasses; /* Number of large size classes. */
 unsigned	nhclasses; /* Number of huge size classes. */
@@ -100,8 +100,12 @@ arena_run_comp(const arena_chunk_map_misc_t *a, const arena_chunk_map_misc_t *b)
 rb_gen(static UNUSED, arena_run_tree_, arena_run_tree_t, arena_chunk_map_misc_t,
     rb_link, arena_run_comp)
 
+#ifdef JEMALLOC_JET
+#undef run_quantize_floor
+#define	run_quantize_floor JEMALLOC_N(run_quantize_floor_impl)
+#endif
 static size_t
-run_quantize(size_t size)
+run_quantize_floor(size_t size)
 {
 	size_t qsize;
 
@@ -119,13 +123,18 @@ run_quantize(size_t size)
 	 */
 	qsize = index2size(size2index(size - large_pad + 1) - 1) + large_pad;
 	if (qsize <= SMALL_MAXCLASS + large_pad)
-		return (run_quantize(size - large_pad));
+		return (run_quantize_floor(size - large_pad));
 	assert(qsize <= size);
 	return (qsize);
 }
+#ifdef JEMALLOC_JET
+#undef run_quantize_floor
+#define	run_quantize_floor JEMALLOC_N(run_quantize_floor)
+run_quantize_t *run_quantize_floor = JEMALLOC_N(run_quantize_floor_impl);
+#endif
 
 static size_t
-run_quantize_next(size_t size)
+run_quantize_ceil_hard(size_t size)
 {
 	size_t large_run_size_next;
 
@@ -158,10 +167,14 @@ run_quantize_next(size_t size)
 	}
 }
 
+#ifdef JEMALLOC_JET
+#undef run_quantize_ceil
+#define	run_quantize_ceil JEMALLOC_N(run_quantize_ceil_impl)
+#endif
 static size_t
-run_quantize_first(size_t size)
+run_quantize_ceil(size_t size)
 {
-	size_t qsize = run_quantize(size);
+	size_t qsize = run_quantize_floor(size);
 
 	if (qsize < size) {
 		/*
@@ -172,10 +185,15 @@ run_quantize_first(size_t size)
 		 * search would potentially find sufficiently aligned available
 		 * memory somewhere lower.
 		 */
-		qsize = run_quantize_next(size);
+		qsize = run_quantize_ceil_hard(size);
 	}
 	return (qsize);
 }
+#ifdef JEMALLOC_JET
+#undef run_quantize_ceil
+#define	run_quantize_ceil JEMALLOC_N(run_quantize_ceil)
+run_quantize_t *run_quantize_ceil = JEMALLOC_N(run_quantize_ceil_impl);
+#endif
 
 JEMALLOC_INLINE_C int
 arena_avail_comp(const arena_chunk_map_misc_t *a,
@@ -183,9 +201,9 @@ arena_avail_comp(const arena_chunk_map_misc_t *a,
 {
 	int ret;
 	uintptr_t a_miscelm = (uintptr_t)a;
-	size_t a_qsize = run_quantize(arena_miscelm_is_key(a) ?
+	size_t a_qsize = run_quantize_floor(arena_miscelm_is_key(a) ?
 	    arena_miscelm_key_size_get(a) : arena_miscelm_size_get(a));
-	size_t b_qsize = run_quantize(arena_miscelm_size_get(b));
+	size_t b_qsize = run_quantize_floor(arena_miscelm_size_get(b));
 
 	/*
 	 * Compare based on quantized size rather than size, in order to sort
@@ -1081,7 +1099,7 @@ arena_chunk_ralloc_huge_expand(arena_t *arena, void *chunk, size_t oldsize,
 static arena_run_t *
 arena_run_first_best_fit(arena_t *arena, size_t size)
 {
-	size_t search_size = run_quantize_first(size);
+	size_t search_size = run_quantize_ceil(size);
 	arena_chunk_map_misc_t *key = arena_miscelm_key_create(search_size);
 	arena_chunk_map_misc_t *miscelm =
 	    arena_avail_tree_nsearch(&arena->runs_avail, key);
diff --git a/test/unit/run_quantize.c b/test/unit/run_quantize.c
new file mode 100644
index 00000000..aff4056b
--- /dev/null
+++ b/test/unit/run_quantize.c
@@ -0,0 +1,157 @@
+#include "test/jemalloc_test.h"
+
+TEST_BEGIN(test_small_run_size)
+{
+	unsigned nbins, i;
+	size_t sz, run_size;
+	size_t mib[4];
+	size_t miblen = sizeof(mib) / sizeof(size_t);
+
+	/*
+	 * Iterate over all small size classes, get their run sizes, and verify
+	 * that the quantized size is the same as the run size.
+	 */
+
+	sz = sizeof(unsigned);
+	assert_d_eq(mallctl("arenas.nbins", &nbins, &sz, NULL, 0), 0,
+	    "Unexpected mallctl failure");
+
+	assert_d_eq(mallctlnametomib("arenas.bin.0.run_size", mib, &miblen), 0,
+	    "Unexpected mallctlnametomib failure");
+	for (i = 0; i < nbins; i++) {
+		mib[2] = i;
+		sz = sizeof(size_t);
+		assert_d_eq(mallctlbymib(mib, miblen, &run_size, &sz, NULL, 0),
+		    0, "Unexpected mallctlbymib failure");
+		assert_zu_eq(run_size, run_quantize_floor(run_size),
+		    "Small run quantization should be a no-op (run_size=%zu)",
+		    run_size);
+		assert_zu_eq(run_size, run_quantize_ceil(run_size),
+		    "Small run quantization should be a no-op (run_size=%zu)",
+		    run_size);
+	}
+}
+TEST_END
+
+TEST_BEGIN(test_large_run_size)
+{
+	bool cache_oblivious;
+	unsigned nlruns, i;
+	size_t sz, run_size_prev, ceil_prev;
+	size_t mib[4];
+	size_t miblen = sizeof(mib) / sizeof(size_t);
+
+	/*
+	 * Iterate over all large size classes, get their run sizes, and verify
+	 * that the quantized size is the same as the run size.
+	 */
+
+	sz = sizeof(bool);
+	assert_d_eq(mallctl("config.cache_oblivious", &cache_oblivious, &sz,
+	    NULL, 0), 0, "Unexpected mallctl failure");
+
+	sz = sizeof(unsigned);
+	assert_d_eq(mallctl("arenas.nlruns", &nlruns, &sz, NULL, 0), 0,
+	    "Unexpected mallctl failure");
+
+	assert_d_eq(mallctlnametomib("arenas.lrun.0.size", mib, &miblen), 0,
+	    "Unexpected mallctlnametomib failure");
+	for (i = 0; i < nlruns; i++) {
+		size_t lrun_size, run_size, floor, ceil;
+
+		mib[2] = i;
+		sz = sizeof(size_t);
+		assert_d_eq(mallctlbymib(mib, miblen, &lrun_size, &sz, NULL, 0),
+		    0, "Unexpected mallctlbymib failure");
+		run_size = cache_oblivious ? lrun_size + PAGE : lrun_size;
+		floor = run_quantize_floor(run_size);
+		ceil = run_quantize_ceil(run_size);
+
+		assert_zu_eq(run_size, floor,
+		    "Large run quantization should be a no-op for precise "
+		    "size (lrun_size=%zu, run_size=%zu)", lrun_size, run_size);
+		assert_zu_eq(run_size, ceil,
+		    "Large run quantization should be a no-op for precise "
+		    "size (lrun_size=%zu, run_size=%zu)", lrun_size, run_size);
+
+		if (i > 0) {
+			assert_zu_eq(run_size_prev, run_quantize_floor(run_size
+			    - PAGE), "Floor should be a precise size");
+			if (run_size_prev < ceil_prev) {
+				assert_zu_eq(ceil_prev, run_size,
+				    "Ceiling should be a precise size "
+				    "(run_size_prev=%zu, ceil_prev=%zu, "
+				    "run_size=%zu)", run_size_prev, ceil_prev,
+				    run_size);
+			}
+		}
+		run_size_prev = floor;
+		ceil_prev = run_quantize_ceil(run_size + PAGE);
+	}
+}
+TEST_END
+
+TEST_BEGIN(test_monotonic)
+{
+	bool cache_oblivious;
+	unsigned nbins, nlruns, i;
+	size_t sz, max_run_size, floor_prev, ceil_prev;
+
+	/*
+	 * Iterate over all run sizes and verify that
+	 * run_quantize_{floor,ceil}() are monotonic.
+	 */
+
+	sz = sizeof(bool);
+	assert_d_eq(mallctl("config.cache_oblivious", &cache_oblivious, &sz,
+	    NULL, 0), 0, "Unexpected mallctl failure");
+
+	sz = sizeof(unsigned);
+	assert_d_eq(mallctl("arenas.nbins", &nbins, &sz, NULL, 0), 0,
+	    "Unexpected mallctl failure");
+
+	sz = sizeof(unsigned);
+	assert_d_eq(mallctl("arenas.nlruns", &nlruns, &sz, NULL, 0), 0,
+	    "Unexpected mallctl failure");
+
+	max_run_size = (large_maxclass > small_maxrun) ? large_maxclass :
+	    small_maxrun;
+
+	floor_prev = 0;
+	ceil_prev = 0;
+	for (i = 1; i < max_run_size >> LG_PAGE; i++) {
+		size_t run_size, floor, ceil;
+
+		run_size = i << LG_PAGE;
+		floor = run_quantize_floor(run_size);
+		ceil = run_quantize_ceil(run_size);
+
+		assert_zu_le(floor, run_size,
+		    "Floor should be <= (floor=%zu, run_size=%zu, ceil=%zu)",
+		    floor, run_size, ceil);
+		assert_zu_ge(ceil, run_size,
+		    "Ceiling should be >= (floor=%zu, run_size=%zu, ceil=%zu)",
+		    floor, run_size, ceil);
+
+		assert_zu_le(floor_prev, floor, "Floor should be monotonic "
+		    "(floor_prev=%zu, floor=%zu, run_size=%zu, ceil=%zu)",
+		    floor_prev, floor, run_size, ceil);
+		assert_zu_le(ceil_prev, ceil, "Ceiling should be monotonic "
+		    "(floor=%zu, run_size=%zu, ceil_prev=%zu, ceil=%zu)",
+		    floor, run_size, ceil_prev, ceil);
+
+		floor_prev = floor;
+		ceil_prev = ceil;
+	}
+}
+TEST_END
+
+int
+main(void)
+{
+
+	return (test(
+	    test_small_run_size,
+	    test_large_run_size,
+	    test_monotonic));
+}