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Posted to commits@cassandra.apache.org by "Michael Burman (JIRA)" <ji...@apache.org> on 2018/03/03 09:08:00 UTC

[jira] [Commented] (CASSANDRA-14281) Reduce contention on DecayingEstimatedHistogramReservoir

    [ https://issues.apache.org/jira/browse/CASSANDRA-14281?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16384570#comment-16384570 ] 

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

I've changed the ticket description to match the discussion here. The reduced amount of histograms updates during writes should be separate work.

> 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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