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From "Michael Burman (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-14281) Reduce contention on DecayingEstimatedHistogramReservoir
Date Sat, 03 Mar 2018 11:22:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-14281?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16384622#comment-16384622
] 

Michael Burman commented on CASSANDRA-14281:
--------------------------------------------

Well, there's certainly still too much contention. The performance does not really scale with
16 cores machine. 

> Reduce contention on DecayingEstimatedHistogramReservoir
> --------------------------------------------------------
>
>                 Key: CASSANDRA-14281
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-14281
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Michael Burman
>            Assignee: Michael Burman
>            Priority: Major
>
> Currently, the DecayingEstimatedHistogramReservoir acquires a lock for each update operation,
which causes a contention if there are more than one thread updating the histogram. This impacts
scalability when using larger machines. We should make it lock-free as much as possible and
also avoid a single CAS-update from blocking all the concurrent threads from making an update.



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