Change CacheMetrics to be quicker

We change it so that each cache has an individual CacheMetric, instead
of having one global CacheMetric. This means that when a cache tries to
increment a counter it does not need to go through so many indirections.

synapse/util/caches/__init__.py

@@ -24,11 +24,21 @@ DEBUG_CACHES = False
 metrics = synapse.metrics.get_metrics_for("synapse.util.caches")
 
 caches_by_name = {}
-cache_counter = metrics.register_cache(
-    "cache",
-    lambda: {(name,): len(caches_by_name[name]) for name in caches_by_name.keys()},
-    labels=["name"],
-)
+# cache_counter = metrics.register_cache(
+#     "cache",
+#     lambda: {(name,): len(caches_by_name[name]) for name in caches_by_name.keys()},
+#     labels=["name"],
+# )
+
+
+def register_cache(name, cache):
+    caches_by_name[name] = cache
+    return metrics.register_cache(
+        "cache",
+        lambda: len(cache),
+        name,
+    )
+
 
 _string_cache = LruCache(int(5000 * CACHE_SIZE_FACTOR))
 caches_by_name["string_cache"] = _string_cache

synapse/util/caches/descriptors.py

@@ -22,7 +22,7 @@ from synapse.util.logcontext import (
     PreserveLoggingContext, preserve_context_over_deferred, preserve_context_over_fn
 )
 
-from . import caches_by_name, DEBUG_CACHES, cache_counter
+from . import DEBUG_CACHES, register_cache
 
 from twisted.internet import defer
 
@@ -43,6 +43,15 @@ CACHE_SIZE_FACTOR = float(os.environ.get("SYNAPSE_CACHE_FACTOR", 0.1))
 
 
 class Cache(object):
+    __slots__ = (
+        "cache",
+        "max_entries",
+        "name",
+        "keylen",
+        "sequence",
+        "thread",
+        "metrics",
+    )
 
     def __init__(self, name, max_entries=1000, keylen=1, lru=True, tree=False):
         if lru:
@@ -59,7 +68,7 @@ class Cache(object):
         self.keylen = keylen
         self.sequence = 0
         self.thread = None
-        caches_by_name[name] = self.cache
+        self.metrics = register_cache(name, self.cache)
 
     def check_thread(self):
         expected_thread = self.thread
@@ -74,10 +83,10 @@ class Cache(object):
     def get(self, key, default=_CacheSentinel):
         val = self.cache.get(key, _CacheSentinel)
         if val is not _CacheSentinel:
-            cache_counter.inc_hits(self.name)
+            self.metrics.inc_hits()
             return val
 
-        cache_counter.inc_misses(self.name)
+        self.metrics.inc_misses()
 
         if default is _CacheSentinel:
             raise KeyError()

synapse/util/caches/dictionary_cache.py

@@ -15,7 +15,7 @@
 
 from synapse.util.caches.lrucache import LruCache
 from collections import namedtuple
-from . import caches_by_name, cache_counter
+from . import register_cache
 import threading
 import logging
 
@@ -43,7 +43,7 @@ class DictionaryCache(object):
             __slots__ = []
 
         self.sentinel = Sentinel()
-        caches_by_name[name] = self.cache
+        self.metrics = register_cache(name, self.cache)
 
     def check_thread(self):
         expected_thread = self.thread
@@ -58,7 +58,7 @@ class DictionaryCache(object):
     def get(self, key, dict_keys=None):
         entry = self.cache.get(key, self.sentinel)
         if entry is not self.sentinel:
-            cache_counter.inc_hits(self.name)
+            self.metrics.inc_hits()
 
             if dict_keys is None:
                 return DictionaryEntry(entry.full, dict(entry.value))
@@ -69,7 +69,7 @@ class DictionaryCache(object):
                     if k in entry.value
                 })
 
-        cache_counter.inc_misses(self.name)
+        self.metrics.inc_misses()
         return DictionaryEntry(False, {})
 
     def invalidate(self, key):

synapse/util/caches/expiringcache.py

@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from synapse.util.caches import cache_counter, caches_by_name
+from synapse.util.caches import register_cache
 
 import logging
 
@@ -49,7 +49,7 @@ class ExpiringCache(object):
 
         self._cache = {}
 
-        caches_by_name[cache_name] = self._cache
+        self.metrics = register_cache(cache_name, self._cache)
 
     def start(self):
         if not self._expiry_ms:
@@ -78,9 +78,9 @@ class ExpiringCache(object):
     def __getitem__(self, key):
         try:
             entry = self._cache[key]
-            cache_counter.inc_hits(self._cache_name)
+            self.metrics.inc_hits()
         except KeyError:
-            cache_counter.inc_misses(self._cache_name)
+            self.metrics.inc_misses()
             raise
 
         if self._reset_expiry_on_get:

synapse/util/caches/stream_change_cache.py

@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from synapse.util.caches import cache_counter, caches_by_name
+from synapse.util.caches import register_cache
 
 
 from blist import sorteddict
@@ -42,7 +42,7 @@ class StreamChangeCache(object):
         self._cache = sorteddict()
         self._earliest_known_stream_pos = current_stream_pos
         self.name = name
-        caches_by_name[self.name] = self._cache
+        self.metrics = register_cache(self.name, self._cache)
 
         for entity, stream_pos in prefilled_cache.items():
             self.entity_has_changed(entity, stream_pos)
@@ -53,19 +53,19 @@ class StreamChangeCache(object):
         assert type(stream_pos) is int
 
         if stream_pos < self._earliest_known_stream_pos:
-            cache_counter.inc_misses(self.name)
+            self.metrics.inc_misses()
             return True
 
         latest_entity_change_pos = self._entity_to_key.get(entity, None)
         if latest_entity_change_pos is None:
-            cache_counter.inc_hits(self.name)
+            self.metrics.inc_hits()
             return False
 
         if stream_pos < latest_entity_change_pos:
-            cache_counter.inc_misses(self.name)
+            self.metrics.inc_misses()
             return True
 
-        cache_counter.inc_hits(self.name)
+        self.metrics.inc_hits()
         return False
 
     def get_entities_changed(self, entities, stream_pos):
@@ -82,10 +82,10 @@ class StreamChangeCache(object):
                 self._cache[k] for k in keys[i:]
             ).intersection(entities)
 
-            cache_counter.inc_hits(self.name)
+            self.metrics.inc_hits()
         else:
             result = entities
-            cache_counter.inc_misses(self.name)
+            self.metrics.inc_misses()
 
         return result