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https://issues.apache.org/jira/browse/CASSANDRA-9242?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16552136#comment-16552136
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Joseph Lynch commented on CASSANDRA-9242:
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Do we think it's worth documenting that an alternative workaround that doesn't
break JVM tooling is to simply mount {{/tmp}} on an in memory tmpfs?
As I'm writing the troubleshooting docs page (CASSANDRA-14553) it's somewhat
tricky not having standard JVM tooling like {{jstat}} around to help debug e.g.
heap pressure.
> Add PerfDisableSharedMem to default JVM params
> ----------------------------------------------
>
> Key: CASSANDRA-9242
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9242
> Project: Cassandra
> Issue Type: Improvement
> Components: Configuration
> Reporter: Matt Stump
> Assignee: Ariel Weisberg
> Priority: Major
> Fix For: 2.2.0 beta 1
>
>
> We should add PerfDisableSharedMem to default JVM params. The JVM will save
> stats to a memory mapped file when reaching a safepoint. This is performed
> synchronously and the JVM remains paused while this action takes place.
> Occasionally the OS will stall the calling thread while this happens
> resulting in significant impact to worst case JVM pauses. By disabling the
> save in the JVM these mysterious multi-second pauses disappear.
> The behavior is outlined in [this
> article|http://www.evanjones.ca/jvm-mmap-pause.html]. Another manifestation
> is significant time spent in sys during GC pauses. In [the linked
> test|http://cstar.datastax.com/graph?stats=762d9c2a-eace-11e4-8236-42010af0688f&metric=gc_max_ms&operation=1_write&smoothing=1&show_aggregates=true&xmin=0&xmax=110.77&ymin=0&ymax=10421.4]
> you'll notice multiple seconds spent in sys during the longest pauses.
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