bdeggleston commented on code in PR #2144:
URL: https://github.com/apache/cassandra/pull/2144#discussion_r1127012212
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src/java/org/apache/cassandra/service/accord/AccordStateCache.java:
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@@ -149,17 +145,12 @@ public NamedMap(String name)
}
}
- public final Map<Object, Node<?, ?>> active = new HashMap<>();
private final Map<Object, Node<?, ?>> cache = new HashMap<>();
- private final Map<Object, WriteOnlyGroup<?, ?>> pendingWriteOnly = new
HashMap<>();
- private final Set<Instance<?, ?>> instances = new HashSet<>();
-
- private final NamedMap<Object, Future<?>> loadFutures = new
NamedMap<>("loadFutures");
- private final NamedMap<Object, Future<?>> saveFutures = new
NamedMap<>("saveFutures");
+ private final Set<Instance<?, ?, ?>> instances = new HashSet<>();
- private final NamedMap<Object, Future<Data>> readFutures = new
NamedMap<>("readFutures");
- private final NamedMap<Object, Future<?>> writeFutures = new
NamedMap<>("writeFutures");
+ private final NamedMap<Object, AsyncResult<Void>> saveResults = new
NamedMap<>("saveResults");
+ private int linked = 0;
Review Comment:
So from the expected cache behavior perspective, we should be inserting into
this list as soon as it becomes unreferenced, because it’s tracking the least
recently used objects
Jumping over a handful of stragglers isn’t optimal, but still qualifies as
negligible I think.
The full/empty case is more of a concern though, and something that would be
more likely with smaller cache sizes. I haven't thought of any solutions that
don't cause their own problems.
The extra link idea doesn’t really work because the cache passively updates
it’s state by iterating over the linked list, so that additional link would
never be made.
WDYT about calling maybeEvict periodically, instead as part of
reference/release? That would at least bound the amount of wasted work in
extreme cases without adding any complexity to the cache
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