Need help on long minor GC pause

[Wüthrich Jörg]

Hi Avinash,

If it turns out to be a fragmentation issue, you might want to consider 
upgrading to a newer java version, because 1.6u25 and above have serious 
improvements concerning fragmentation 
(http://blog.ragozin.info/2011/10/java-cg-hotspots-cms-and-heap.html).

One place where I saw very long pauses with fragmentation was when 
concurrent mode failures occurred. I am not sure if fragmentation 
affects minor GCs so much.

You might also want to follow another lead: swapping. GC logs also 
contain the "|Times:user=2.19sys=1.35,real=385.50secs]" in the end of 
the lines. If "real" is much longer than "user"+"sys" your system might 
be swapping.|
|||
Regards,
Jörg

|Am 11.09.2013 10:24, schrieb Avinash Mishra:
> Hi folks,
>
> We are facing a strange issue where the minor GC gets stuck for 
> several seconds:
>
> 734827.324: [GC 639235K->587610K(1042048K), 2.4140118 secs]
> 734846.488: [GC 640090K->589859K(1042048K), 22.1046232 secs]
> 734949.577: [GC 642339K->590078K(1042048K), 12.2527731 secs]
> 735045.592: [GC 642558K->591084K(1042048K), 0.1158979 secs]
> Our Java configuration is something like this:
>
> java -Xms1024m -Xmx1024m -XX:+UseConcMarkSweepGC -cp %MY_CLASSPATH% 
> com.myclass
>
> We are using Java 1.6u24 and the application is running on a Windows 
> 2003 server.
>
> The issue is specific to a couple of servers at a customer site and 
> nowhere else. The servers here run fine for up to some 45 days when 
> the issue shows up.
>
> From the logs(above) it seems that there is plenty of old space 
> available on heap so we have ruled out concurrent failures. We are 
> looking into fragmentation as the potential root cause. We have 
> enabled these traces to confirm if we have a fragmentation issue
>
> -XX:+PrintGCDetails
> -XX:+PrintPromotionFailure
> -XX:PrintFLSStatistics=1
>
> From these logs we are monitoring "Max chunk available" and look for a 
> decrease in trend to determine if the servers are heading towards a 
> fragmentation problem. Please let me know if anything else is required 
> to confirm on fragmentation issue and if there is a a way to confirm 
> it sooner instead of waiting for couple of months.
>
> Please let me know if you have any other pointers on potential root cause.
>
> Thanks,
> Avinash
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