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From "Ariel Weisberg (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6809) Compressed Commit Log
Date Tue, 17 Mar 2015 19:31:39 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6809?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14365867#comment-14365867
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Ariel Weisberg commented on CASSANDRA-6809:
-------------------------------------------

I think what Benedict is describing where we only deallocate if the queue has more than one
available (and > 3) is good idea. If the knob is set too low it might give better behavior
at steady state?

I would still be +1 since I think it won't matter once we multi-thread compression (and I
intend to do that for 3.1).

> Compressed Commit Log
> ---------------------
>
>                 Key: CASSANDRA-6809
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6809
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Benedict
>            Assignee: Branimir Lambov
>            Priority: Minor
>              Labels: docs-impacting, performance
>             Fix For: 3.0
>
>         Attachments: ComitLogStress.java, logtest.txt
>
>
> It seems an unnecessary oversight that we don't compress the commit log. Doing so should
improve throughput, but some care will need to be taken to ensure we use as much of a segment
as possible. I propose decoupling the writing of the records from the segments. Basically
write into a (queue of) DirectByteBuffer, and have the sync thread compress, say, ~64K chunks
every X MB written to the CL (where X is ordinarily CLS size), and then pack as many of the
compressed chunks into a CLS as possible.



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