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From "Yu Li (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14522) Document and/or disable hsperfdata GC pauses
Date Wed, 07 Oct 2015 16:57:27 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14522?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14947206#comment-14947206
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Yu Li commented on HBASE-14522:
-------------------------------

Above comment is a little bit ambiguous, so allow me to quote from the cassandra JIRA:
{quote}
The default JVM flag -XX:+PerfDisableSharedMem will cause the following tools JVM
to stop working. jps, jstack, jinfo, jmc, jcmd as well as 3rd party tools like Jolokia.
{quote}

Since tools like jps, jstack, jinfo, etc. are necessary for maintenance and problem debugging,
maybe adding the option into hbase-env.sh but not as default a better idea?

> 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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