diff --git a/Objects/obmalloc.c b/Objects/obmalloc.c
index 76ff6f9c99bc9c..8f88e60f576d78 100644
--- a/Objects/obmalloc.c
+++ b/Objects/obmalloc.c
@@ -1397,6 +1397,114 @@ static int arena_map_bot_count;
 static arena_map_bot_t arena_map_root;
 #endif
 
+/* arena_map_cache[...] is a directly mapped cache for the result of
+ * address_in_range(pool).  The two low order bits correspond to the return
+ * value of address_in_range(), 00 == no entry, 01 == small, 10 == large.  For
+ * the cache, small means it was allocated by obmalloc, large is allocated by
+ * other malloc.  The high order bits are the pool address.
+ */
+#define CACHE_BITS 7
+#define CACHE_SIZE (1<<CACHE_BITS)
+#define CACHE_MASK (CACHE_SIZE - 1)
+
+#define CACHE_VALUE_EMPTY 0
+/* pool address contains large object (outside arena) */
+#define CACHE_VALUE_LARGE 1
+/* pool address contains small object (inside arena) */
+#define CACHE_VALUE_SMALL 2
+#define CACHE_VALUE_MASK (CACHE_VALUE_LARGE | CACHE_VALUE_SMALL)
+
+static uintptr_t arena_map_cache[CACHE_SIZE];
+
+/* turn off for benchmarks, some overhead */
+#define CACHE_STATS
+
+#ifdef CACHE_STATS
+static unsigned int cache_hits;
+static unsigned int cache_collisions;
+static unsigned int cache_lookups;
+#endif
+
+static inline uintptr_t
+pool_number(poolp pool)
+{
+    return AS_UINT(pool) >> POOL_BITS;
+}
+
+static inline uintptr_t
+cache_index(poolp pool)
+{
+    uintptr_t pool_number = AS_UINT(pool) >> POOL_BITS;
+    return pool_number & CACHE_MASK;
+}
+
+static inline void
+cache_put(poolp pool, int value)
+{
+    int idx = cache_index(pool);
+    uintptr_t entry = AS_UINT(pool) | value;
+    assert((entry & ~CACHE_VALUE_MASK) == AS_UINT(pool));
+#ifdef CACHE_STATS
+    if (arena_map_cache[idx] != entry) {
+        if (arena_map_cache[idx] != 0) {
+            cache_collisions++;
+        }
+        arena_map_cache[idx] = entry;
+    }
+#else
+    arena_map_cache[idx] = entry;
+#endif
+}
+
+static uintptr_t
+cache_get(poolp pool)
+{
+    int idx = cache_index(pool);
+    uintptr_t entry = arena_map_cache[idx];
+#ifdef CACHE_STATS
+    cache_lookups++;
+#endif
+    if ((entry & ~CACHE_VALUE_MASK) != AS_UINT(pool)) {
+        /* entry exists but pool addr doesn't match */
+        return CACHE_VALUE_EMPTY;
+    }
+#ifdef CACHE_STATS
+    cache_hits++;
+#endif
+    return (entry & CACHE_VALUE_MASK);
+}
+
+static inline void
+cache_clear(poolp pool)
+{
+    int idx = cache_index(pool);
+    arena_map_cache[idx] = 0;
+}
+
+#if 0
+/* setup cache for all pools in arena */
+static void
+cache_mark_arena(struct arena_object *arenaobj)
+{
+    uintptr_t base = (uintptr_t)_Py_ALIGN_UP(arenaobj->address, POOL_SIZE);
+    for (uint i = 0; i < arenaobj->ntotalpools; i++) {
+        cache_put((poolp)base, CACHE_VALUE_SMALL);
+        base += POOL_SIZE;
+    }
+}
+#endif
+
+/* clear cache for all pools in arena */
+static void
+cache_clear_arena(struct arena_object *arenaobj)
+{
+    uintptr_t base = (uintptr_t)_Py_ALIGN_UP(arenaobj->address, POOL_SIZE);
+    for (uint i = 0; i < arenaobj->ntotalpools; i++) {
+        cache_clear((poolp)base);
+        base += POOL_SIZE;
+    }
+}
+
 /* Return a pointer to a bottom tree node, return NULL if it doesn't exist or
  * it cannot be created */
 static arena_map_bot_t *
@@ -1627,6 +1735,8 @@ new_arena(void)
     }
     arenaobj->ntotalpools = arenaobj->nfreepools;
 
+    //cache_mark_arena(arenaobj);
+
     return arenaobj;
 }
 
@@ -1639,7 +1749,19 @@ new_arena(void)
 static bool
 address_in_range(void *p, poolp pool)
 {
-    return arena_map_is_used(p);
+    bool in_arena;
+    int cache_value = cache_get(pool);
+    if (cache_value == CACHE_VALUE_EMPTY) {
+        in_arena = arena_map_is_used(p);
+        uintptr_t cache_value = in_arena ? CACHE_VALUE_SMALL : CACHE_VALUE_LARGE;
+        cache_put(pool, cache_value);
+        //assert(cache_get(pool) == cache_value);
+    }
+    else {
+        in_arena = cache_value == CACHE_VALUE_SMALL;
+    }
+    assert(in_arena == arena_map_is_used(p));
+    return in_arena;
 }
 #else
 /*
@@ -1889,6 +2011,7 @@ allocate_from_new_pool(uint size)
     return bp;
 }
 
+
 /* pymalloc allocator
 
    Return a pointer to newly allocated memory if pymalloc allocated memory.
@@ -1940,7 +2063,7 @@ pymalloc_alloc(void *ctx, size_t nbytes)
          */
         bp = allocate_from_new_pool(size);
     }
-
+    //cache_put(bp, CACHE_VALUE_SMALL);
     return (void *)bp;
 }
 
@@ -1955,6 +2078,7 @@ _PyObject_Malloc(void *ctx, size_t nbytes)
 
     ptr = PyMem_RawMalloc(nbytes);
     if (ptr != NULL) {
+        //cache_put(ptr, CACHE_VALUE_LARGE);
         raw_allocated_blocks++;
     }
     return ptr;
@@ -1975,6 +2099,7 @@ _PyObject_Calloc(void *ctx, size_t nelem, size_t elsize)
 
     ptr = PyMem_RawCalloc(nelem, elsize);
     if (ptr != NULL) {
+        //cache_put(ptr, CACHE_VALUE_LARGE);
         raw_allocated_blocks++;
     }
     return ptr;
@@ -2082,6 +2207,7 @@ insert_to_freepool(poolp pool)
 #if WITH_PYMALLOC_RADIX_TREE
         /* mark arena region as not under control of obmalloc */
         arena_map_mark_used(ao->address, 0);
+        cache_clear_arena(ao);
 #endif
 
         /* Free the entire arena. */
@@ -2236,6 +2362,7 @@ _PyObject_Free(void *ctx, void *p)
     if (UNLIKELY(!pymalloc_free(ctx, p))) {
         /* pymalloc didn't allocate this address */
         PyMem_RawFree(p);
+        cache_clear(POOL_ADDR(p));
         raw_allocated_blocks--;
     }
 }
@@ -3061,6 +3188,11 @@ _PyObject_DebugMallocStats(FILE *out)
                       sizeof(arena_map_bot_t) * arena_map_bot_count);
 #endif
     (void)printone(out, "Total", total);
+
+#ifdef CACHE_STATS
+    fprintf(out, "cache hits %d lookups %d collisions %d %.3f\n", cache_hits,
+            cache_lookups, cache_collisions, ((double)cache_hits)/(cache_lookups));
+#endif
     return 1;
 }