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Issue #22847: Improve method cache efficiency.

This commit is contained in:
Antoine Pitrou 2014-11-15 00:56:27 +01:00
parent 59f0682190
commit 2a40e36739
2 changed files with 38 additions and 4 deletions
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2
Misc/NEWS
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@ -10,6 +10,8 @@ Release date: TBA
Core and Builtins
-----------------
- Issue #22847: Improve method cache efficiency.
- Issue #22335: Fix crash when trying to enlarge a bytearray to 0x7fffffff
bytes on a 32-bit platform.

40
Objects/typeobject.c
View File

@ -14,10 +14,11 @@
MCACHE_MAX_ATTR_SIZE, since it might be a problem if very large
strings are used as attribute names. */
#define MCACHE_MAX_ATTR_SIZE 100
#define MCACHE_SIZE_EXP 9
#define MCACHE_SIZE_EXP 12
#define MCACHE_HASH(version, name_hash) \
(((unsigned int)(version) * (unsigned int)(name_hash)) \
>> (8*sizeof(unsigned int) - MCACHE_SIZE_EXP))
(((unsigned int)(version) ^ (unsigned int)(name_hash)) \
& ((1 << MCACHE_SIZE_EXP) - 1))
#define MCACHE_HASH_METHOD(type, name) \
MCACHE_HASH((type)->tp_version_tag, \
((PyASCIIObject *)(name))->hash)
@ -35,6 +36,14 @@ struct method_cache_entry {
static struct method_cache_entry method_cache[1 << MCACHE_SIZE_EXP];
static unsigned int next_version_tag = 0;
#define MCACHE_STATS 0
#if MCACHE_STATS
static size_t method_cache_hits = 0;
static size_t method_cache_misses = 0;
static size_t method_cache_collisions = 0;
#endif
/* alphabetical order */
_Py_IDENTIFIER(__abstractmethods__);
_Py_IDENTIFIER(__class__);
@ -165,6 +174,18 @@ PyType_ClearCache(void)
Py_ssize_t i;
unsigned int cur_version_tag = next_version_tag - 1;
#if MCACHE_STATS
size_t total = method_cache_hits + method_cache_collisions + method_cache_misses;
fprintf(stderr, "-- Method cache hits = %zd (%d%%)\n",
method_cache_hits, (int) (100.0 * method_cache_hits / total));
fprintf(stderr, "-- Method cache true misses = %zd (%d%%)\n",
method_cache_misses, (int) (100.0 * method_cache_misses / total));
fprintf(stderr, "-- Method cache collisions = %zd (%d%%)\n",
method_cache_collisions, (int) (100.0 * method_cache_collisions / total));
fprintf(stderr, "-- Method cache size = %zd KB\n",
sizeof(method_cache) / 1024);
#endif
for (i = 0; i < (1 << MCACHE_SIZE_EXP); i++) {
method_cache[i].version = 0;
Py_CLEAR(method_cache[i].name);
@ -2708,8 +2729,12 @@ _PyType_Lookup(PyTypeObject *type, PyObject *name)
/* fast path */
h = MCACHE_HASH_METHOD(type, name);
if (method_cache[h].version == type->tp_version_tag &&
method_cache[h].name == name)
method_cache[h].name == name) {
#if MCACHE_STATS
method_cache_hits++;
#endif
return method_cache[h].value;
}
}
/* Look in tp_dict of types in MRO */
@ -2743,6 +2768,13 @@ _PyType_Lookup(PyTypeObject *type, PyObject *name)
method_cache[h].version = type->tp_version_tag;
method_cache[h].value = res; /* borrowed */
Py_INCREF(name);
assert(((PyASCIIObject *)(name))->hash != -1);
#if MCACHE_STATS
if (method_cache[h].name != Py_None && method_cache[h].name != name)
method_cache_collisions++;
else
method_cache_misses++;
#endif
Py_DECREF(method_cache[h].name);
method_cache[h].name = name;
}