Major GC occurring before CMS occupancy fraction

Bernd Eckenfels ecki at zusammenkunft.net
Fri Dec 5 01:18:44 UTC 2014


Hello,

I see 

ParNews from 5GB/5GB -> 140MB 
CMS 4GB/10GB -> 1GB/10GB

That would fit the 40% mark, but your args are different.

I suspect some of the pools like code cache, perm gen or similiar
beeing full. I am not sure if this is only logged with
-XX:+PrintGCCause, but you can try. You might even be able to observe
it with "jstat -gccause" live.

Gruss
Bernd




Am Tue, 2 Dec 2014 10:38:22 -0500
schrieb nitin sharma <kumarsharma.nitin at gmail.com>:

> Hi Bernd,
> 
> Apologies for such a late response. i got carried away in other
> priorities ...
> 
> PFA the truncated GC log for 24 hrs.. Kindly assist me to understand
> why CMS collection is triggered well before "initial-occupancy"
> fraction value.
> 
> Regards,
> Nitin Kumar Sharma.
> 
> 
> On Tue, Nov 18, 2014 at 8:13 PM, Bernd Eckenfels
> <ecki at zusammenkunft.net> wrote:
> 
> > Hello,
> >
> > you need to provide verbose GC logs so we can say anything on that.
> > But be aware that you might not get much help on ancient Java :)
> >
> > Can you try to set the initial perm size to the maximum size, to
> > make sure resizes in this area do not trigger GC. And are you sure
> > you are not confronted with RMI DGC runs?
> >
> > Gruss
> > Bernd
> >
> >  Am Tue, 18
> > Nov 2014 12:24:23 -0500 schrieb nitin sharma
> > <kumarsharma.nitin at gmail.com>:
> >
> > > hi,
> > >
> > > I am facing the same issue.. We are using JDK 1.6. 0_23 and have
> > > set Occupancy Fraction to 80% but i can see CMS triggered at much
> > > below ration (around 53%)..
> > >
> > > is there a solution for same?
> > >
> > > I have used "-XX:CMSInitiatingOccupancyFraction=80
> > > -XX:+UseCMSInitiatingOccupancyOnly" option...
> > >
> > > complete JVM argument set ==>
> > >
> > > /usr/java/jdk1.6.0_23/bin/java -server -Xms16384m -Xmx16384m
> > > -XX:PermSize=512m -XX:MaxPermSize=1024m -XX:CompileThreshold=8000
> > > -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCDateStamps
> > > -XX:+PrintGCTimeStamps -XX:+UseParNewGC -XX:MaxNewSize=6144m
> > > -XX:NewSize=6144m -XX:+UseConcMarkSweepGC -XX:ParallelGCThreads=4
> > > -XX:+CMSClassUnloadingEnabled -XX:+CMSPermGenSweepingEnabled
> > > -XX:CMSInitiatingOccupancyFraction=80
> > > -XX:+UseCMSInitiatingOccupancyOnly -DUseSunHttpHandler=true
> > > -XX:+HeapDumpOnOutOfMemoryError
> > >
> > >
> > >
> > > Regards,
> > > Nitin Kumar Sharma.
> > >
> >
> 


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