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https://issues.apache.org/jira/browse/SOLR-8241?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15558521#comment-15558521
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Ben Manes commented on SOLR-8241:
---------------------------------
I can take a stab at tests, but its unclear what to include other than basic
operations. Otherwise I'd defer to the library for deeper testing, e.g. scan
resistance and efficiency. In those areas writing tests is for the author to
have assurance that the library does what it claims. I'd prefer if someone
obtained production traces instead, which I think would show you an interesting
hit rate curve for how the policies stack up.
I'm pretty sure the current warming, which populates with the hottest entries
first, should be good enough. Since reads dominate writes, the hot entries will
quickly have a high frequency by the time an eviction is triggered. We can try
to give the first few hot entries a small bump too, by adding a few accesses,
to add an extra nudge.
> Evaluate W-TinyLfu cache
> ------------------------
>
> Key: SOLR-8241
> URL: https://issues.apache.org/jira/browse/SOLR-8241
> Project: Solr
> Issue Type: Wish
> Components: search
> Reporter: Ben Manes
> Priority: Minor
> Attachments: SOLR-8241.patch, SOLR-8241.patch
>
>
> SOLR-2906 introduced an LFU cache and in-progress SOLR-3393 makes it O(1).
> The discussions seem to indicate that the higher hit rate (vs LRU) is offset
> by the slower performance of the implementation. An original goal appeared to
> be to introduce ARC, a patented algorithm that uses ghost entries to retain
> history information.
> My analysis of Window TinyLfu indicates that it may be a better option. It
> uses a frequency sketch to compactly estimate an entry's popularity. It uses
> LRU to capture recency and operate in O(1) time. When using available
> academic traces the policy provides a near optimal hit rate regardless of the
> workload.
> I'm getting ready to release the policy in Caffeine, which Solr already has a
> dependency on. But, the code is fairly straightforward and a port into Solr's
> caches instead is a pragmatic alternative. More interesting is what the
> impact would be in Solr's workloads and feedback on the policy's design.
> https://github.com/ben-manes/caffeine/wiki/Efficiency
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