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From "Edward Capriolo (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-1181) kinder gentler compaction
Date Wed, 23 Jun 2010 16:28:53 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1181?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12881733#action_12881733
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Edward Capriolo commented on CASSANDRA-1181:
--------------------------------------------

I think ThreadPriority will help, however CPU Priority is not directly linked to IO scheduling.
I believe between the the statistics cassandra keeps we could accomplish something adaptive.
Also if we want a solution that is not 100% java pure we can read /proc/diskstats and use
actual disk utilization to be adaptive.

All these methods I suggested fall apart if non-compaction traffic is thrashing the disk,
but if that were the case the node was not healthy in the first place.

> kinder gentler compaction
> -------------------------
>
>                 Key: CASSANDRA-1181
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1181
>             Project: Cassandra
>          Issue Type: Task
>            Reporter: Jonathan Ellis
>            Assignee: Brandon Williams
>             Fix For: 0.7
>
>         Attachments: CompactionManager.java
>
>
> I suggested this in a ML thread but it seems that nobody actually tried it.  I think
it's worth following up on:
> You could try setting the compaction thread to a lower priority.  You could add a thread
priority to NamedThreadPool, and pass that up from CompactionExecutor constructor.  According
to http://www.javamex.com/tutorials/threads/priority_what.shtml you have to run as root and
add a JVM option to get this to work.
> In particular, Brandon saw stress.py read latencies spike to 100ms during [anti]compaction
on a 2 core machine.  I'd like to see if this can mitigate that.

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