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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6142) Remove multithreaded compaction
Date Fri, 25 Oct 2013 00:41:02 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6142?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13804861#comment-13804861
] 

Jonathan Ellis commented on CASSANDRA-6142:
-------------------------------------------

Posted 2.0 fixes to https://github.com/jbellis/cassandra/commits/6142-2.0.  Note that b959e8ff3bccd3437de70d33da91307ab9c12a19
is a different, less-invasive approach than the one taken for trunk.

> 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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