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From "Vladimir Rodionov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14522) Document and/or disable hsperfdata GC pauses
Date Wed, 07 Oct 2015 04:22:27 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14522?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14946211#comment-14946211
] 

Vladimir Rodionov commented on HBASE-14522:
-------------------------------------------

The work to do is HBase book update. I posted the link to a corresponding CASSANDRA JIRA,
which discusses all the issues, related to this JVM setting. Several JVM performance tools
won't work if the flag is enabled, all of them are listed in the CASSANDRA JIRA. This JIRA
should be committed and new follow up documentation JIRA should be created.

> 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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