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Ben Manes commented on CASSANDRA-10855:
---------------------------------------
{quote}
I've added .executor(MoreExecutors.directExecutor()) - hope I got your
suggestion right.
{quote}
This is good for unit tests to remove asynchronous behavior. My preference is
to not use it in production, especially where latencies matter, by not
penalizing callers with maintenance or removal notification work. Instead
deferring that to FJP should help minimize response times, which I think would
be your preference too. I'm not familiar enough with Cassandra's testing to
know whether its trivial to flag the executor. Usually its pretty trivial,
especially when DI like Guice is used.
{quote}
There are a couple of cache.asMap() calls. Would it be an option to eagerly
create the AsMapView, Values and EntrySet instances in LocalAsyncLoadingCache
to get around the ternaries in asMap(), values(), entrySet() and keySet?
{quote}
{{LocalAsyncLoadingCache}} isn't used by Cassandra (a cache that returns
{{CompletableFuture}}. Given the ternaries are null checks to lazily create
views, as is common in the Java Collections, I don't think its a measurable
penalty to keep.
{quote}
Do you have some micro-benchmarks in place to actually test against the
previous implementation(s)?
{quote}
For concurrent throughput (JMH) see these
[benchmarks|https://github.com/ben-manes/caffeine/wiki/Benchmarks]. They show a
refinements over CLHM, with a primary benefit in write. Since the cache now
supports memoization, the Cassandra APIs might benefit from using a computation
instead of racy _get-load-put_ calls.
For hit rates see these
[simulations|https://github.com/ben-manes/caffeine/wiki/Efficiency]. They show
W-TinyLFU improves upon LRU by taking into account frequency.
I'll send a PR to your branch when I get a chance to go through the rest of the
comments. Thanks!
> Use Caffeine (W-TinyLFU) for on-heap caches
> -------------------------------------------
>
> Key: CASSANDRA-10855
> URL: https://issues.apache.org/jira/browse/CASSANDRA-10855
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Ben Manes
> Labels: performance
> Attachments: CASSANDRA-10855.patch, CASSANDRA-10855.patch
>
>
> Cassandra currently uses
> [ConcurrentLinkedHashMap|https://code.google.com/p/concurrentlinkedhashmap]
> for performance critical caches (key, counter) and Guava's cache for
> non-critical (auth, metrics, security). All of these usages have been
> replaced by [Caffeine|https://github.com/ben-manes/caffeine], written by the
> author of the previously mentioned libraries.
> The primary incentive is to switch from LRU policy to W-TinyLFU, which
> provides [near optimal|https://github.com/ben-manes/caffeine/wiki/Efficiency]
> hit rates. It performs particularly well in database and search traces, is
> scan resistant, and as adds a very small time/space overhead to LRU.
> Secondarily, Guava's caches never obtained similar
> [performance|https://github.com/ben-manes/caffeine/wiki/Benchmarks] to CLHM
> due to some optimizations not being ported over. This change results in
> faster reads and not creating garbage as a side-effect.
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