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https://issues.apache.org/jira/browse/CASSANDRA-11452?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15238285#comment-15238285
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Ben Manes commented on CASSANDRA-11452:
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For the case of 128mb cache with 190mb data set, the degredation may be due to
Caffeine's lazily initialization of the sketch. This is done when cache is at
least 50% full to avoid penalizing by setting an artificially high bound. This
change was suggested on the other Cassandra ticket to also avoid the
unnecessary penalty when the cache exceeds the data size, e.g. due to
expiration and a safety threshold that is never reachable.
For maximum weight the expected number of entries is unknown. This probably
causes it to resize more frequently in order to keep the sketch's error rate
constant, causing it to lose the history. When the cache is full the entry
count won't differ all that much, so it begins to capture the frequency
histogram but the trace ends before its made up for the poor start. This might
be why the smaller sizes did well and the larger ones suffered.
In the latest SNAPSHOT the {{initialCapacity}} setting will pre-size the sketch
in addition to the hash table
([commit|https://github.com/ben-manes/caffeine/commit/9711f8bb75cd6feb060ac4f4a58ad27ea0065deb]).
Then if you know the average entry size this problem won't occur.
> 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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