diff --git a/class.c b/class.c
index 8f11f45..ec587a1 100644
--- a/class.c
+++ b/class.c
@@ -170,6 +170,7 @@ class_alloc(VALUE flags, VALUE klass)
 
     RCLASS_REFINED_CLASS(obj) = Qnil;
     RCLASS_EXT(obj)->allocator = 0;
+    MEMZERO(&RCLASS_EXT(obj)->cache, struct rb_meth_cache, 1);
     return (VALUE)obj;
 }
 
@@ -510,6 +511,7 @@ make_singleton_class(VALUE obj)
 {
     VALUE orig_class = RBASIC(obj)->klass;
     VALUE klass = rb_class_boot(orig_class);
+    rb_method_cache_copy(orig_class, klass);
 
     FL_SET(klass, FL_SINGLETON);
     RBASIC_SET_CLASS(obj, klass);
diff --git a/gc.c b/gc.c
index 776d97d..1cf6ead 100644
--- a/gc.c
+++ b/gc.c
@@ -1588,6 +1588,7 @@ obj_free(rb_objspace_t *objspace, VALUE obj)
 	}
 	rb_class_remove_from_module_subclasses(obj);
 	rb_class_remove_from_super_subclasses(obj);
+	rb_method_cache_clear(obj);
 	if (RANY(obj)->as.klass.ptr)
 	    xfree(RANY(obj)->as.klass.ptr);
 	RANY(obj)->as.klass.ptr = NULL;
@@ -1658,6 +1659,7 @@ obj_free(rb_objspace_t *objspace, VALUE obj)
 	}
 	rb_class_remove_from_module_subclasses(obj);
 	rb_class_remove_from_super_subclasses(obj);
+	rb_method_cache_clear(obj);
 	xfree(RANY(obj)->as.klass.ptr);
 	RANY(obj)->as.klass.ptr = NULL;
 	break;
@@ -1827,6 +1829,9 @@ rb_objspace_each_objects(each_obj_callback *callback, void *data)
 struct os_each_struct {
     size_t num;
     VALUE of;
+#if METHOD_CACHE_STATS
+    int with_hidden_klasses;
+#endif
 };
 
 static int
@@ -1852,6 +1857,25 @@ internal_object_p(VALUE obj)
     return 1;
 }
 
+#if METHOD_CACHE_STATS
+static int
+hidden_class_p(VALUE obj)
+{
+    RVALUE *p = (RVALUE *)obj;
+
+    if (p->as.basic.flags) {
+	switch (BUILTIN_TYPE(p)) {
+	  case T_ICLASS:
+	    return 1;
+	  case T_CLASS:
+	    if (FL_TEST(p, FL_SINGLETON))
+	      return 1;
+	}
+    }
+    return 0;
+}
+#endif
+
 int
 rb_objspace_internal_object_p(VALUE obj)
 {
@@ -1866,7 +1890,11 @@ os_obj_of_i(void *vstart, void *vend, size_t stride, void *data)
 
     for (; p != pend; p++) {
 	volatile VALUE v = (VALUE)p;
+#if METHOD_CACHE_STATS
+	if (!internal_object_p(v) || (oes->with_hidden_klasses && hidden_class_p(v))) {
+#else
 	if (!internal_object_p(v)) {
+#endif
 	    if (!oes->of || rb_obj_is_kind_of(v, oes->of)) {
 		rb_yield(v);
 		oes->num++;
@@ -1878,12 +1906,19 @@ os_obj_of_i(void *vstart, void *vend, size_t stride, void *data)
 }
 
 static VALUE
+#if METHOD_CACHE_STATS
+os_obj_of(VALUE of, VALUE whk)
+#else
 os_obj_of(VALUE of)
+#endif
 {
     struct os_each_struct oes;
 
     oes.num = 0;
     oes.of = of;
+#if METHOD_CACHE_STATS
+    oes.with_hidden_klasses = RTEST(whk);
+#endif
     rb_objspace_each_objects(os_obj_of_i, &oes);
     return SIZET2NUM(oes.num);
 }
@@ -1924,6 +1959,23 @@ os_obj_of(VALUE of)
  *
  */
 
+#if METHOD_CACHE_STATS
+static VALUE
+os_each_obj(int argc, VALUE *argv, VALUE os)
+{
+    VALUE args[2];
+
+    if (argc == 0) {
+	args[0] = 0;
+	args[1] = Qnil;
+    }
+    else {
+	rb_scan_args(argc, argv, "02", &args[0], &args[1]);
+    }
+    RETURN_ENUMERATOR(os, 2, args);
+    return os_obj_of(args[0], args[1]);
+}
+#else
 static VALUE
 os_each_obj(int argc, VALUE *argv, VALUE os)
 {
@@ -1938,6 +1990,7 @@ os_each_obj(int argc, VALUE *argv, VALUE os)
     RETURN_ENUMERATOR(os, 1, &of);
     return os_obj_of(of);
 }
+#endif
 
 /*
  *  call-seq:
diff --git a/internal.h b/internal.h
index 1f41d23..15c715c 100644
--- a/internal.h
+++ b/internal.h
@@ -261,6 +261,58 @@ typedef unsigned long rb_serial_t;
 #define SERIALT2NUM ULONG2NUM
 #endif
 
+#if !defined(METHOD_CACHE_STATS)
+#define METHOD_CACHE_STATS 0
+#endif
+
+#if METHOD_CACHE_STATS
+struct rb_meth_cache_stats {
+	size_t sum_capa;
+	size_t sum_used;
+	size_t sum_undefs;
+	size_t alloced;
+	size_t not_empty;
+	size_t copies;
+	size_t resets;
+	size_t insertions;
+	size_t created;
+	size_t destroyed;
+	size_t copy_alloced;
+	size_t copy_reset;
+};
+extern struct rb_meth_cache_stats rb_meth_cache;
+VALUE rb_method_cache_stats(int argc, VALUE* argv, VALUE obj);
+#endif
+
+struct rb_meth_cache_entry {
+    ID mid;
+    uintptr_t me;
+    VALUE defined_class;
+};
+
+/* valid values for MCACHE_INLINED are 1, 2, 3 and 4 */
+#ifndef MCACHE_INLINED
+#define MCACHE_INLINED 3
+#endif
+#ifndef MCACHE_RESET_FREES_COPY
+#define MCACHE_RESET_FREES_COPY 1
+#endif
+struct rb_meth_cache {
+    rb_serial_t method_state;
+    rb_serial_t class_serial;
+    int size, capa;
+    int is_copy;
+#if METHOD_CACHE_STATS
+    int undefs;
+    size_t resets;
+    size_t insertions;
+#endif
+    union {
+	struct rb_meth_cache_entry *ntries;
+	struct rb_meth_cache_entry n[MCACHE_INLINED];
+    } e;
+};
+
 struct rb_classext_struct {
     struct st_table *iv_index_tbl;
     struct st_table *iv_tbl;
@@ -277,8 +329,37 @@ struct rb_classext_struct {
     VALUE origin;
     VALUE refined_class;
     rb_alloc_func_t allocator;
+    struct rb_meth_cache cache;
 };
 
+static inline void
+rb_method_cache_clear(VALUE klass)
+{
+    struct rb_classext_struct *ext = RCLASS(klass)->ptr;
+    if (ext->cache.capa > MCACHE_INLINED && ext->cache.e.ntries) {
+	xfree(ext->cache.e.ntries);
+	ext->cache.e.ntries = NULL;
+#if METHOD_CACHE_STATS
+	rb_meth_cache.alloced--;
+	rb_meth_cache.sum_capa -= ext->cache.capa;
+	rb_meth_cache.destroyed++;
+#endif
+	ext->cache.capa = 0;
+    }
+#if METHOD_CACHE_STATS
+    if (ext->cache.is_copy) {
+	ext->cache.is_copy = 0;
+	rb_meth_cache.copies--;
+    }
+    if (ext->cache.size > 0) {
+	rb_meth_cache.not_empty--;
+	rb_meth_cache.sum_used -= ext->cache.size;
+	rb_meth_cache.sum_undefs -= ext->cache.undefs;
+	ext->cache.size = 0;
+    }
+#endif
+}
+
 struct method_table_wrapper {
     st_table *tbl;
     size_t serial;
@@ -790,6 +871,7 @@ VALUE rb_extract_keywords(VALUE *orighash);
 /* vm_method.c */
 void Init_eval_method(void);
 int rb_method_defined_by(VALUE obj, ID mid, VALUE (*cfunc)(ANYARGS));
+void rb_method_cache_copy(VALUE from, VALUE to);
 
 /* miniprelude.c, prelude.c */
 void Init_prelude(void);
diff --git a/vm.c b/vm.c
index 212f7b0..185d3f8 100644
--- a/vm.c
+++ b/vm.c
@@ -2492,6 +2492,9 @@ Init_VM(void)
     rb_undef_alloc_func(rb_cRubyVM);
     rb_undef_method(CLASS_OF(rb_cRubyVM), "new");
     rb_define_singleton_method(rb_cRubyVM, "stat", vm_stat, -1);
+#if METHOD_CACHE_STATS
+    rb_define_singleton_method(rb_cRubyVM, "method_cache_stats", rb_method_cache_stats, -1);
+#endif
 
     /* FrozenCore (hidden) */
     fcore = rb_class_new(rb_cBasicObject);
diff --git a/vm_method.c b/vm_method.c
index 2270359..8d85e3f 100644
--- a/vm_method.c
+++ b/vm_method.c
@@ -2,15 +2,6 @@
  * This file is included by vm.c
  */
 
-#ifndef GLOBAL_METHOD_CACHE_SIZE
-#define GLOBAL_METHOD_CACHE_SIZE 0x800
-#endif
-#ifndef GLOBAL_METHOD_CACHE_MASK
-#define GLOBAL_METHOD_CACHE_MASK 0x7ff
-#endif
-
-#define GLOBAL_METHOD_CACHE_KEY(c,m) ((((c)>>3)^(m))&GLOBAL_METHOD_CACHE_MASK)
-#define GLOBAL_METHOD_CACHE(c,m) (global_method_cache + GLOBAL_METHOD_CACHE_KEY(c,m))
 #include "method.h"
 
 #define NOEX_NOREDEF 0
@@ -29,15 +20,324 @@ static void rb_vm_check_redefinition_opt_method(const rb_method_entry_t *me, VAL
 #define singleton_undefined idSingleton_method_undefined
 #define attached            id__attached__
 
-struct cache_entry {
-    rb_serial_t method_state;
-    rb_serial_t class_serial;
-    ID mid;
-    rb_method_entry_t* me;
-    VALUE defined_class;
-};
+#if METHOD_CACHE_STATS
+struct rb_meth_cache_stats rb_meth_cache;
+#endif
+
+typedef struct rb_meth_cache_entry cache_entry_t;
+
+#define METHOD_ENTRY(entry) ((rb_method_entry_t*)((entry)->me & ~1))
+#define COLLISION(entry) ((entry).me & 1)
+#define HASH(id) (id ^ (id >> 3))
+
+static void rb_mcache_resize(struct rb_meth_cache *cache);
+static void
+rb_mcache_insert(struct rb_meth_cache *cache, ID id, uintptr_t me, VALUE defined_class)
+{
+    int mask, pos, dlt;
+    cache_entry_t *ent;
+#if METHOD_CACHE_STATS
+    if (cache->size == 0) {
+	rb_meth_cache.not_empty++;
+    }
+#endif
+    if (cache->capa == MCACHE_INLINED) {
+	if (cache->size < MCACHE_INLINED) {
+	    ent = cache->e.n;
+	    pos = cache->size;
+	    goto found;
+	}
+	rb_mcache_resize(cache);
+    } else if (cache->capa / 4 * 3 <= cache->size) {
+	rb_mcache_resize(cache);
+    }
+    mask = cache->capa - 1;
+    pos = HASH(id) & mask;
+
+    ent = cache->e.ntries;
+    if (ent[pos].mid == 0) {
+	goto found;
+    }
+    ent[pos].me |= 1; /* set collision */
+    dlt = (id % mask) | 1;
+    for(;;) {
+	pos = (pos + dlt) & mask;
+	if (ent[pos].mid == 0) {
+	    goto found;
+	}
+	ent[pos].me |= 1;
+    }
+found:
+    ent += pos;
+    ent->defined_class = defined_class;
+    ent->mid = id;
+    ent->me = me;
+    cache->size++;
+#if METHOD_CACHE_STATS
+    cache->insertions++;
+    cache->undefs += me == 0;
+    rb_meth_cache.sum_undefs += me == 0;
+    rb_meth_cache.sum_used++;
+    rb_meth_cache.insertions++;
+#endif
+}
+
+#define MCACHE_MIN_SIZE 8
+#define MCACHE_MIN_SHRINK 16
+#define MCACHE_SHRINK_TRIGGER 16
+#define MCACHE_SHRINK_BOUND 4
+static void
+rb_mcache_resize(struct rb_meth_cache *cache)
+{
+    struct rb_meth_cache tmp;
+    cache_entry_t *entries;
+    int i;
+
+    MEMZERO(&tmp, struct rb_meth_cache, 1);
+    tmp.method_state = cache->method_state;
+    tmp.class_serial = cache->class_serial;
+#if METHOD_CACHE_STATS
+    tmp.resets = cache->resets;
+    tmp.insertions = cache->insertions;
+    rb_meth_cache.sum_undefs -= cache->undefs;
+    if (cache->size > 0) {
+	rb_meth_cache.not_empty--;
+    }
+#endif
+    if (cache->capa == MCACHE_INLINED) {
+	tmp.capa = MCACHE_MIN_SIZE;
+	entries = cache->e.n;
+    }
+    else {
+	tmp.capa = cache->capa * 2;
+	entries = cache->e.ntries;
+#if METHOD_CACHE_STATS
+	rb_meth_cache.sum_capa -= cache->capa;
+#endif
+    }
+redo:
+    tmp.e.ntries = xcalloc(tmp.capa, sizeof(cache_entry_t));
+    for(i = 0; i < cache->capa; i++) {
+	if (entries[i].mid && (entries[i].me & ~1)) {
+	    cache_entry_t *ent = &entries[i];
+	    rb_mcache_insert(&tmp, ent->mid, ent->me & ~1, ent->defined_class);
+	}
+    }
+    /* deal with lots of cached method_missing */
+    if (tmp.size < tmp.capa / MCACHE_SHRINK_TRIGGER && tmp.capa > MCACHE_MIN_SHRINK) {
+	    xfree(tmp.e.ntries);
+#if METHOD_CACHE_STATS
+	    rb_meth_cache.sum_used -= tmp.size;
+	    if (tmp.size > 0) {
+		rb_meth_cache.not_empty--;
+	    }
+#endif
+	    while(tmp.size < tmp.capa / MCACHE_SHRINK_BOUND && tmp.capa > MCACHE_MIN_SHRINK) {
+		    tmp.capa /= 2;
+	    }
+	    tmp.size = 0;
+	    goto redo;
+    }
+#if METHOD_CACHE_STATS
+    rb_meth_cache.sum_used -= cache->size;
+    rb_meth_cache.sum_capa += tmp.capa;
+    if (cache->capa == MCACHE_INLINED) {
+	rb_meth_cache.alloced++;
+	rb_meth_cache.created++;
+    }
+#endif
+    if (cache->capa > MCACHE_INLINED) {
+	xfree(cache->e.ntries);
+    }
+    *cache = tmp;
+}
+
+static inline void
+rb_mcache_reset(struct rb_meth_cache *cache, rb_serial_t class_serial)
+{
+#if METHOD_CACHE_STATS
+    cache->resets++;
+    rb_meth_cache.resets++;
+    rb_meth_cache.sum_used -= cache->size;
+    rb_meth_cache.sum_undefs -= cache->undefs;
+    cache->undefs = 0;
+    if (cache->size > 0) {
+	rb_meth_cache.not_empty--;
+    }
+#endif
+    if (cache->is_copy) {
+#if METHOD_CACHE_STATS
+	rb_meth_cache.copies--;
+#endif
+	cache->is_copy = 0;
+#if MCACHE_RESET_FREES_COPY
+	if (cache->capa > MCACHE_INLINED && cache->e.ntries != NULL) {
+	    xfree(cache->e.ntries);
+	    cache->e.ntries = NULL;
+#if METHOD_CACHE_STATS
+	    rb_meth_cache.copy_reset++;
+	    rb_meth_cache.sum_capa -= cache->capa;
+	    rb_meth_cache.alloced--;
+#endif
+	    cache->capa = 0;
+	}
+#endif
+    }
+    cache->method_state = GET_GLOBAL_METHOD_STATE();
+    cache->class_serial = class_serial;
+    cache->size = 0;
+    if (cache->capa == 0 || cache->capa == MCACHE_INLINED) {
+	cache->capa = MCACHE_INLINED;
+	MEMZERO(cache->e.n, cache_entry_t, MCACHE_INLINED);
+    }
+    else if (cache->e.ntries != NULL) {
+	MEMZERO(cache->e.ntries, cache_entry_t, cache->capa);
+    }
+}
+
+static inline cache_entry_t*
+rb_mcache_find(struct rb_meth_cache *cache, ID id)
+{
+    if (cache->capa == MCACHE_INLINED) {
+	if (cache->e.n[0].mid == id) return &cache->e.n[0];
+#if MCACHE_INLINED > 1
+	if (cache->e.n[1].mid == id) return &cache->e.n[1];
+#endif
+#if MCACHE_INLINED > 2
+	if (cache->e.n[2].mid == id) return &cache->e.n[2];
+#endif
+#if MCACHE_INLINED > 3
+	if (cache->e.n[3].mid == id) return &cache->e.n[3];
+#endif
+#if MCACHE_INLINED > 4
+#error "Are you serious about such huge MCACHE_INLINED?"
+#endif
+	return NULL;
+    }
+    else {
+	cache_entry_t *ent = cache->e.ntries;
+	int mask = cache->capa - 1;
+	int pos = HASH(id) & mask;
+	int dlt;
+	if (ent[pos].mid == id) return ent + pos;
+	if (!COLLISION(ent[pos])) return NULL;
+	dlt = (id % mask) | 1;
+	for(;;) {
+	    pos = (pos + dlt) & mask;
+	    if (ent[pos].mid == id) return ent + pos;
+	    if (!COLLISION(ent[pos])) return NULL;
+	}
+    }
+}
+
+void
+rb_method_cache_copy(VALUE from, VALUE to)
+{
+    struct rb_meth_cache *from_cache = &RCLASS_EXT(from)->cache, *to_cache = &RCLASS_EXT(to)->cache;
+    if (!from_cache->size) return;
+
+    if (to_cache->capa > MCACHE_INLINED && to_cache->e.ntries) {
+	xfree(to_cache->e.ntries);
+#if METHOD_CACHE_STATS
+	rb_meth_cache.alloced--;
+	rb_meth_cache.sum_capa -= to_cache->capa;
+	rb_meth_cache.sum_used -= to_cache->size;
+	rb_meth_cache.sum_undefs -= to_cache->undefs;
+    }
+    if (to_cache->is_copy) {
+	rb_meth_cache.copies--;
+    }
+    if (to_cache->size > 0) {
+	rb_meth_cache.not_empty--;
+    }
+    if (from_cache->size > 0) {
+	rb_meth_cache.not_empty++;
+#endif
+    }
+    to_cache->capa = from_cache->capa;
+    to_cache->size = from_cache->size;
+    to_cache->method_state = from_cache->method_state;
+    to_cache->class_serial = RCLASS_SERIAL(to);
+    to_cache->is_copy = 1;
+    if (from_cache->capa > MCACHE_INLINED) {
+	to_cache->e.ntries = xcalloc(to_cache->capa, sizeof(cache_entry_t));
+	MEMCPY(to_cache->e.ntries, from_cache->e.ntries, cache_entry_t, from_cache->capa);
+#if METHOD_CACHE_STATS
+	rb_meth_cache.alloced++;
+	rb_meth_cache.sum_capa += to_cache->capa;
+	rb_meth_cache.copy_alloced++;
+#endif
+    } else {
+	MEMCPY(to_cache->e.n, from_cache->e.n, cache_entry_t, MCACHE_INLINED);
+    }
+#if METHOD_CACHE_STATS
+    to_cache->undefs = from_cache->undefs;
+    rb_meth_cache.sum_used += to_cache->size;
+    rb_meth_cache.sum_undefs += to_cache->undefs;
+    rb_meth_cache.copies++;
+#endif
+}
+
+#if METHOD_CACHE_STATS
+VALUE
+rb_method_cache_stats(int argc, VALUE* argv, VALUE obj)
+{
+    ID used, capa, copy, alloced, resets, insertions, undefs;
+    ID created, destroyed, copy_alloced, copy_reset, not_empty;
+    VALUE res = rb_hash_new();
+    CONST_ID(used, "used");
+    CONST_ID(capa, "capa");
+    CONST_ID(copy, "copy");
+    CONST_ID(not_empty, "not_empty");
+    CONST_ID(alloced, "alloced");
+    CONST_ID(resets, "resets");
+    CONST_ID(insertions, "insertions");
+    CONST_ID(undefs, "undefs");
+    CONST_ID(created, "created");
+    CONST_ID(destroyed, "destroyed");
+    CONST_ID(copy_alloced, "copy_alloced");
+    CONST_ID(copy_reset, "copy_reset");
+
+    rb_check_arity(argc, 0, 1);
+    if (argc == 1) {
+	VALUE klass = argv[0];
+	struct rb_meth_cache *cache;
+	int type = BUILTIN_TYPE(klass);
+	if (type != T_CLASS && type != T_ICLASS) {
+	    Check_Type(klass, T_CLASS);
+	}
+	cache = &RCLASS_EXT(klass)->cache;
+	rb_hash_aset(res, ID2SYM(used), INT2FIX(cache->size));
+	rb_hash_aset(res, ID2SYM(undefs),  INT2FIX(cache->undefs));
+	if (cache->capa <= MCACHE_INLINED) {
+	    rb_hash_aset(res, ID2SYM(capa), INT2FIX(0));
+	    rb_hash_aset(res, ID2SYM(alloced),  INT2FIX(0));
+	} else {
+	    rb_hash_aset(res, ID2SYM(capa), INT2FIX(cache->capa));
+	    rb_hash_aset(res, ID2SYM(alloced),  INT2FIX(1));
+	}
+	rb_hash_aset(res, ID2SYM(not_empty), INT2FIX(cache->size > 0));
+	rb_hash_aset(res, ID2SYM(copy), INT2FIX(cache->is_copy));
+	rb_hash_aset(res, ID2SYM(resets), SIZET2NUM(cache->resets));
+	rb_hash_aset(res, ID2SYM(insertions), SIZET2NUM(cache->insertions));
+    } else if (argc == 0) {
+	rb_hash_aset(res, ID2SYM(used), SIZET2NUM(rb_meth_cache.sum_used));
+	rb_hash_aset(res, ID2SYM(undefs),  SIZET2NUM(rb_meth_cache.sum_undefs));
+	rb_hash_aset(res, ID2SYM(capa), SIZET2NUM(rb_meth_cache.sum_capa));
+	rb_hash_aset(res, ID2SYM(alloced),  SIZET2NUM(rb_meth_cache.alloced));
+	rb_hash_aset(res, ID2SYM(not_empty), SIZET2NUM(rb_meth_cache.not_empty));
+	rb_hash_aset(res, ID2SYM(copy), SIZET2NUM(rb_meth_cache.copies));
+	rb_hash_aset(res, ID2SYM(resets), SIZET2NUM(rb_meth_cache.resets));
+	rb_hash_aset(res, ID2SYM(insertions), SIZET2NUM(rb_meth_cache.insertions));
+	rb_hash_aset(res, ID2SYM(created),  SIZET2NUM(rb_meth_cache.created));
+	rb_hash_aset(res, ID2SYM(destroyed),  SIZET2NUM(rb_meth_cache.destroyed));
+	rb_hash_aset(res, ID2SYM(copy_alloced),  SIZET2NUM(rb_meth_cache.copy_alloced));
+	rb_hash_aset(res, ID2SYM(copy_reset),  SIZET2NUM(rb_meth_cache.copy_reset));
+    }
+    return res;
+}
+#endif
 
-static struct cache_entry global_method_cache[GLOBAL_METHOD_CACHE_SIZE];
 #define ruby_running (GET_VM()->running)
 /* int ruby_running = 0; */
 
@@ -578,20 +878,11 @@ rb_method_entry_get_without_cache(VALUE klass, ID id,
     }
 
     if (ruby_running) {
-	struct cache_entry *ent;
-	ent = GLOBAL_METHOD_CACHE(klass, id);
-	ent->class_serial = RCLASS_EXT(klass)->class_serial;
-	ent->method_state = GET_GLOBAL_METHOD_STATE();
-	ent->defined_class = defined_class;
-	ent->mid = id;
-
+	struct rb_classext_struct *ext = RCLASS_EXT(klass);
 	if (UNDEFINED_METHOD_ENTRY_P(me)) {
-	    ent->me = 0;
 	    me = 0;
 	}
-	else {
-	    ent->me = me;
-	}
+	rb_mcache_insert(&ext->cache, id, (uintptr_t)me, defined_class);
     }
 
     if (defined_class_ptr)
@@ -617,18 +908,22 @@ rb_method_entry_t *
 rb_method_entry(VALUE klass, ID id, VALUE *defined_class_ptr)
 {
 #if OPT_GLOBAL_METHOD_CACHE
-    struct cache_entry *ent;
-    ent = GLOBAL_METHOD_CACHE(klass, id);
-    if (ent->method_state == GET_GLOBAL_METHOD_STATE() &&
-	ent->class_serial == RCLASS_EXT(klass)->class_serial &&
-	ent->mid == id) {
+    struct rb_classext_struct *ext = RCLASS_EXT(klass);
+    if (ext->cache.method_state != GET_GLOBAL_METHOD_STATE() ||
+	ext->cache.class_serial != ext->class_serial) {
+	rb_mcache_reset(&ext->cache, ext->class_serial);
+    } else {
+	cache_entry_t *ent;
+	ent = rb_mcache_find(&ext->cache, id);
+	if (ent == NULL) goto not_found;
 	if (defined_class_ptr)
 	    *defined_class_ptr = ent->defined_class;
 #if VM_DEBUG_VERIFY_METHOD_CACHE
 	verify_method_cache(klass, id, ent->defined_class, ent->me);
 #endif
-	return ent->me;
+	return METHOD_ENTRY(ent);
     }
+not_found:
 #endif
 
     return rb_method_entry_get_without_cache(klass, id, defined_class_ptr);