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https://issues.apache.org/jira/browse/SOLR-8241?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15802076#comment-15802076
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Ben Manes commented on SOLR-8241:
---------------------------------

I think the tests all passed last I checked with this new SolrCache, but I 
don't think we had made it the default yet so that might be a premature 
statement. If you want to upgrade only the 1.x usage, that would be a safe 
change to extract from this patch (a minor API tweak). If anything the later 
versions also have fewer bugs.

I'd love to see this patch land.

> 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-8241.patch, 
> proposal.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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