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From "Misty Stanley-Jones (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14522) Document and/or disable hsperfdata GC pauses
Date Thu, 08 Oct 2015 05:21:27 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14522?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14948090#comment-14948090
] 

Misty Stanley-Jones commented on HBASE-14522:
---------------------------------------------

OK, please take the status out of 'Patch Available' and someone create at least a rough draft
of an explanation in both places, and then let me know if you need help getting it into the
docs.

> Document and/or disable hsperfdata GC pauses
> --------------------------------------------
>
>                 Key: HBASE-14522
>                 URL: https://issues.apache.org/jira/browse/HBASE-14522
>             Project: HBase
>          Issue Type: Task
>          Components: documentation, Performance
>            Reporter: Nick Dimiduk
>            Assignee: Lars Francke
>         Attachments: HBASE-14522.patch
>
>
> {quote}
> The JVM by default exports statistics by mmap-ing a file in /tmp (hsperfdata). On Linux,
modifying a memory mapped file can block until disk I/O completes, which can be hundreds of
milliseconds. Since the JVM modifies these statistics during garbage collection and safepoints,
this causes pauses that are hundreds of milliseconds long.
> {quote}
> Via [JVM mmap pause|http://www.evanjones.ca/jvm-mmap-pause.html].
> We should add {{-XX:+PerfDisableSharedMem}} to our default options as was apparently
done in CASSANDRA-9242 and/or document the presence of this bug so operators know to use tmpfs.
> Hat-tip [~vrodionov]



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