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Date: Sat, 16 Apr 2016 23:28:25 +0000 (UTC)
From: "Benedict (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (CASSANDRA-11452) Cache implementation using
 LIRS eviction for in-process page cache
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    [ https://issues.apache.org/jira/browse/CASSANDRA-11452?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15244465#comment-15244465 ] 

Benedict commented on CASSANDRA-11452:
--------------------------------------

One more variant for you: instead of random admission, with a similar (or slightly higher) rate, walk an LRU order iterator one step and use the next key's frequency.  After each step, reset the iterator with a 1% chance.

Basically it's the same as random admission but without its blindness.  Could have a bound on frequency, but could be very low, perhaps just 3 to ignore 100% no doubt legit rejections.

Not suggesting you go and do it, just wanted to note it for posterity as I think it's approximately optimal.  Only risk is if your finger gets referenced and bumped to MRU, which could be guarded against.

bq. Thanks a lot for all your help on this =)

My pleasure - this is my idea of fun.


> 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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