diff options
Diffstat (limited to 'synapse/util/caches')
| -rw-r--r-- | synapse/util/caches/lrucache.py | 77 |
1 files changed, 59 insertions, 18 deletions
diff --git a/synapse/util/caches/lrucache.py b/synapse/util/caches/lrucache.py index a21d34fcb4..10b0ec6b75 100644 --- a/synapse/util/caches/lrucache.py +++ b/synapse/util/caches/lrucache.py @@ -17,8 +17,10 @@ from functools import wraps from typing import ( Any, Callable, + Collection, Generic, Iterable, + List, Optional, Type, TypeVar, @@ -57,13 +59,56 @@ class _Node: __slots__ = ["prev_node", "next_node", "key", "value", "callbacks"] def __init__( - self, prev_node, next_node, key, value, callbacks: Optional[set] = None + self, + prev_node, + next_node, + key, + value, + callbacks: Collection[Callable[[], None]] = (), ): self.prev_node = prev_node self.next_node = next_node self.key = key self.value = value - self.callbacks = callbacks or set() + + # Set of callbacks to run when the node gets deleted. We store as a list + # rather than a set to keep memory usage down (and since we expect few + # entries per node, the performance of checking for duplication in a + # list vs using a set is negligible). + # + # Note that we store this as an optional list to keep the memory + # footprint down. Storing `None` is free as its a singleton, while empty + # lists are 56 bytes (and empty sets are 216 bytes, if we did the naive + # thing and used sets). + self.callbacks = None # type: Optional[List[Callable[[], None]]] + + self.add_callbacks(callbacks) + + def add_callbacks(self, callbacks: Collection[Callable[[], None]]) -> None: + """Add to stored list of callbacks, removing duplicates.""" + + if not callbacks: + return + + if not self.callbacks: + self.callbacks = [] + + for callback in callbacks: + if callback not in self.callbacks: + self.callbacks.append(callback) + + def run_and_clear_callbacks(self) -> None: + """Run all callbacks and clear the stored list of callbacks. Used when + the node is being deleted. + """ + + if not self.callbacks: + return + + for callback in self.callbacks: + callback() + + self.callbacks = None class LruCache(Generic[KT, VT]): @@ -177,10 +222,10 @@ class LruCache(Generic[KT, VT]): self.len = synchronized(cache_len) - def add_node(key, value, callbacks: Optional[set] = None): + def add_node(key, value, callbacks: Collection[Callable[[], None]] = ()): prev_node = list_root next_node = prev_node.next_node - node = _Node(prev_node, next_node, key, value, callbacks or set()) + node = _Node(prev_node, next_node, key, value, callbacks) prev_node.next_node = node next_node.prev_node = node cache[key] = node @@ -211,16 +256,15 @@ class LruCache(Generic[KT, VT]): deleted_len = size_callback(node.value) cached_cache_len[0] -= deleted_len - for cb in node.callbacks: - cb() - node.callbacks.clear() + node.run_and_clear_callbacks() + return deleted_len @overload def cache_get( key: KT, default: Literal[None] = None, - callbacks: Iterable[Callable[[], None]] = ..., + callbacks: Collection[Callable[[], None]] = ..., update_metrics: bool = ..., ) -> Optional[VT]: ... @@ -229,7 +273,7 @@ class LruCache(Generic[KT, VT]): def cache_get( key: KT, default: T, - callbacks: Iterable[Callable[[], None]] = ..., + callbacks: Collection[Callable[[], None]] = ..., update_metrics: bool = ..., ) -> Union[T, VT]: ... @@ -238,13 +282,13 @@ class LruCache(Generic[KT, VT]): def cache_get( key: KT, default: Optional[T] = None, - callbacks: Iterable[Callable[[], None]] = (), + callbacks: Collection[Callable[[], None]] = (), update_metrics: bool = True, ): node = cache.get(key, None) if node is not None: move_node_to_front(node) - node.callbacks.update(callbacks) + node.add_callbacks(callbacks) if update_metrics and metrics: metrics.inc_hits() return node.value @@ -260,10 +304,8 @@ class LruCache(Generic[KT, VT]): # We sometimes store large objects, e.g. dicts, which cause # the inequality check to take a long time. So let's only do # the check if we have some callbacks to call. - if node.callbacks and value != node.value: - for cb in node.callbacks: - cb() - node.callbacks.clear() + if value != node.value: + node.run_and_clear_callbacks() # We don't bother to protect this by value != node.value as # generally size_callback will be cheap compared with equality @@ -273,7 +315,7 @@ class LruCache(Generic[KT, VT]): cached_cache_len[0] -= size_callback(node.value) cached_cache_len[0] += size_callback(value) - node.callbacks.update(callbacks) + node.add_callbacks(callbacks) move_node_to_front(node) node.value = value @@ -326,8 +368,7 @@ class LruCache(Generic[KT, VT]): list_root.next_node = list_root list_root.prev_node = list_root for node in cache.values(): - for cb in node.callbacks: - cb() + node.run_and_clear_callbacks() cache.clear() if size_callback: cached_cache_len[0] = 0 |