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From Bernd Fehling <bernd.fehl...@uni-bielefeld.de>
Subject Re: Long STW GCs with Solr Cloud
Date Fri, 17 Jun 2016 08:05:27 GMT


Am 17.06.2016 um 09:06 schrieb Ere Maijala:
> 16.6.2016, 1.41, Shawn Heisey kirjoitti:
>> If you want to continue avoiding G1, you should definitely be using
>> CMS.  My recommendation right now would be to try the G1 settings on my
>> wiki page under the heading "Current experiments" or the CMS settings
>> just below that.
> 
> For what it's worth, we're currently running Shawn's G1 settings slightly modified for
our workload on Java 1.8.0_91 25.91-b14:
> 
> GC_TUNE=" \
> -XX:+UseG1GC \
> -XX:+ParallelRefProcEnabled \
> -XX:G1HeapRegionSize=16m \
> -XX:MaxGCPauseMillis=200 \
> -XX:+UnlockExperimentalVMOptions \
> -XX:G1NewSizePercent=3 \
> -XX:ParallelGCThreads=12 \
> -XX:+UseLargePages \
> -XX:+AggressiveOpts \
> "

-XX:G1NewSizePercent
<Garbage First Garbage Collector Tuning (oracle.com)>
... Sets the percentage of the heap to use as the minimum for the young generation size.
    The default value is 5 percent of your Java heap. ...

So you are reducing the young heap generation size to get a smoother running system.
This is strange, like reducing the bottle below the bottleneck.

Just my 2 cents.

Regards
Bernd

> 
> It seems that our highly varying loads during day vs. night caused some issues leading
to long pauses until I added the G1NewSizePercent (which
> needs +UnlockExperimentalVMOptions). Things are running smoothly and there are reports
that the warnings regarding G1 with Lucene tests don't
> happen anymore with the newer Java versions, but it's of course up to you if you're willing
to take the chance.
> 
> Regards,
> Ere

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