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Ben Manes commented on CASSANDRA-11452:
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Neither the original nor revised papers are clear about that. At first I used
{{>=}} assuming it would be better, but in small traces the change made a
[large
difference|https://github.com/ben-manes/caffeine/commit/3e83411c670ca61a859f0e1ed24e216b847ccd58].
That was prior to the window, so it may be less impactful now. The small
traces are also very specific patterns, whereas the larger ones reflect
real-world use, so that change might be even less noticeable. Another option
might be to recycle the victim in the probation space or degrade to {{>=}} if
we detect the clash. So basically I'd need to analyze it and play with your
test (thanks!) to figure out a good strategy.
An idea that I've wanted to try is if we can detect miss predictions using a
bloom filter. When a candidate is rejected it could be added to this sketch. If
rejected again within the a shorter sample period, then we bypass TinyLFU. This
might mean that the window is too small and could be dynamically sized based on
the feedback. I think it would also help mitigate this collision.
I tried to protect the most likely attach by using a random seed, since I saw
that degredation was possible. But making it more resilient is definitely worth
while and your help here is great.
> Cache implementation using LIRS eviction for in-process page cache
> ------------------------------------------------------------------
>
> Key: CASSANDRA-11452
> URL: https://issues.apache.org/jira/browse/CASSANDRA-11452
> Project: Cassandra
> Issue Type: Improvement
> Components: Local Write-Read Paths
> Reporter: Branimir Lambov
> Assignee: Branimir Lambov
>
> Following up from CASSANDRA-5863, to make best use of caching and to avoid
> having to explicitly marking compaction accesses as non-cacheable, we need a
> cache implementation that uses an eviction algorithm that can better handle
> non-recurring accesses.
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