Merge pull request #3451 from matrix-org/hawkowl/sorteddict-api

Try to not use as much CPU in the cache

2 files changed, 4 insertions, 2 deletions

diff --git a/changelog.d/3447.misc b/changelog.d/3447.misc
new file mode 100644

index 0000000000..e69de29bb2
--- /dev/null
+++ b/changelog.d/3447.misc
diff --git a/synapse/util/caches/stream_change_cache.py b/synapse/util/caches/stream_change_cache.py

index 817118e30f..0fb8620001 100644
--- a/synapse/util/caches/stream_change_cache.py
+++ b/synapse/util/caches/stream_change_cache.py
@@ -78,7 +78,8 @@ class StreamChangeCache(object):
             not_known_entities = set(entities) - set(self._entity_to_key)
 
             result = (
-                set(self._cache.values()[self._cache.bisect_right(stream_pos) :])
+                {self._cache[k] for k in self._cache.islice(
+                    start=self._cache.bisect_right(stream_pos))}
                 .intersection(entities)
                 .union(not_known_entities)
             )
@@ -113,7 +114,8 @@ class StreamChangeCache(object):
         assert type(stream_pos) is int
 
         if stream_pos >= self._earliest_known_stream_pos:
-            return self._cache.values()[self._cache.bisect_right(stream_pos) :]
+            return [self._cache[k] for k in self._cache.islice(
+                start=self._cache.bisect_right(stream_pos))]
         else:
             return None