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From "Marcus Eriksson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6142) Remove multithreaded compaction
Date Thu, 03 Oct 2013 16:32:42 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6142?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13785321#comment-13785321
] 

Marcus Eriksson commented on CASSANDRA-6142:
--------------------------------------------

i tried improving it a while back as well, got basically the same results, yes, we should
remove it

concluded that the best way to improve the speed was to do more compactions in parallel (CASSANDRA-5936
- i should finish that up..)

> Remove multithreaded compaction
> -------------------------------
>
>                 Key: CASSANDRA-6142
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6142
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Jonathan Ellis
>            Assignee: Jonathan Ellis
>            Priority: Minor
>             Fix For: 2.1
>
>
> There is at best a very small sweet spot for multithreaded compaction (ParallelCompactionIterable).
 For large rows, we stall the pipeline and fall back to a single LCR pass.  For small rows,
the overhead of the coordination outweighs the benefits of parallelization (45s to compact
2x1M stress rows with multithreading enabled, vs 35 with it disabled).



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