Can we in a smart way build these best practices into the script, by testing
JVM version and (un)setting some of these automatically based on version? The
solr.in.* config could have a new option GC_TUNE_AUTO="true" and GC_TUNE
commented out. Then if auto is enabled, the bin/solr scripts will decide what
flags to set. Experts can override. Also related is SOLR-6705, some options
should be set automatically only for some JVM versions.
--
Jan Høydahl, search solution architect
Cominvent AS - www.cominvent.com
> 5. nov. 2014 kl. 16.53 skrev Uwe Schindler :
>
> Hi,
>
> I just reviewed the solr.sh.in and solr.cmd.in scripts in solr/bin folder.
> The following was committed but never discussed:
>
> # These GC settings have shown to work well for a number of common Solr
> workloads
> GC_TUNE="-XX:-UseSuperWord \
> -XX:NewRatio=3 \
> -XX:SurvivorRatio=4 \
> -XX:TargetSurvivorRatio=90 \
> -XX:MaxTenuringThreshold=8 \
> -XX:+UseConcMarkSweepGC \
> -XX:+UseParNewGC \
> -XX:ConcGCThreads=4 -XX:ParallelGCThreads=4 \
> -XX:+CMSScavengeBeforeRemark \
> -XX:PretenureSizeThreshold=64m \
> -XX:CMSFullGCsBeforeCompaction=1 \
> -XX:+UseCMSInitiatingOccupancyOnly \
> -XX:CMSInitiatingOccupancyFraction=50 \
> -XX:CMSTriggerPermRatio=80 \
> -XX:CMSMaxAbortablePrecleanTime=6000 \
> -XX:+CMSParallelRemarkEnabled \
> -XX:+ParallelRefProcEnabled \
> -XX:+AggressiveOpts"
>
> This is horrible, because of our experience with Hotspot bugs:
>
> -XX:+AggressiveOpts
> This option is vry risky and speed improvements are marginal. PLEASE
> DON'T DO THIS. If people want the new features they should wait for later
> Java releases and the new features are tested. See several tasks about the
> Java 7 disaster! In fact we had reports at Java 6 times when people had
> enabled this and were affected by the Java 7 GA bugs already in Java 6 and
> corrupted their indexes!!!
>
> -XX:-UseSuperWord
> If you have a Haswell CPU, all other improvements in these command line
> settings are eaten up by this flag! If you have 7u55 at minimum, you should
> never disable this. Things like BooleanFilter and other bitset operations are
> up to 2 times faster with Java 7u55 on Haswell CPUs and later!!! This setting
> only makes sense if you have one of those buggy JDKs (7u40 to 7u51). In all
> other cases this slows down enormous!
> In addition, enabling this option may break JDKs before 7u40 (this option was
> added in 7u40), so breaks:
>> Unrecognized VM option 'UseSuperWord'
>
> It would be good, if we could fix the startup scripts not not have options,
> which may also break with JDK 8 or later!
>
> Uwe
>
> -
> Uwe Schindler
> H.-H.-Meier-Allee 63, D-28213 Bremen
> http://www.thetaphi.de
> eMail: u...@thetaphi.de
>
>
>
>
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