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From Rainer Jung <>
Subject Re: Problem with JVM, and Tomcat tuning
Date Fri, 15 Jun 2007 19:46:42 GMT
Give us a look at your hotspot error files.

Do they look very close to each other, or do they show very different 
stacks as the reason for the crash?

If double free is really the reason it won't be caused by a pure Java 
Tomcat, instead it could be native libs integrated into your webapps by 
JNI or a bug between the JVM and your platform.

Nevertheless a view at your hotspot error files should give a hint.

A second thing: since some of your JVM options are very advanced, 
consider upgrading to Java 1.5.0_12. JVM updates are usually low risk 
and easy to do and most of the patch releases enhance stability of the 
more advanced GC options.



Jacob Bunk Nielsen wrote:
> Hi
> I'm running Tomcat 6.0.13 on Sun Java6 and Linux. I upgraded from
> Tomcat 5.5.17 and Java5 update 9 a couple of weeks ago.
> I experience random crashes of the JVM on a daily basis. It simply
> fails with segmentation faults, double frees and similar. Are any of
> you experiencing similar problems? I had the same problems with Java5
> and Tomcat 5.5, but less often.
> If I submit a bug report with Sun I get a reply that I should contact
> Apache because the problem seems to be triggered by Tomcat. Is anyone
> at Apache interested in those hs_err_PID.log files generated by the
> JVM?
> So, how would I go about avoiding to trigger these sorts of problems?
> It is a production system and I'm not very happy about it being down
> almost daily due to bugs in the JVM.
> I should add that I run my fairly memory consuming application on a 32
> bit server with 4 GB of physical memory and 8 GB of swap space and
> with CATALINA_OPTS set as:
> CATALINA_OPTS=-Djava.awt.headless=true -server -Xms512m -Xmx2g
>  -verbose:gc -XX:+PrintGCTimeStamps -XX:+UseConcMarkSweepGC
>  -XX:+CMSIncrementalMode -XX:+CMSIncrementalPacing -XX:+UseTLAB
>  -XX:+UsePerfData -XX:NewSize=128m -XX:MaxNewSize=128m
>  -XX:MaxTenuringThreshold=0 -XX:SurvivorRatio=1024 -Xincgc
> I tried some even more agressive garbage collector settings a while
> back because I was experiencing long pauses while the garbage
> collector was running, but I kept triggering loads of segmentation
> faults. This is the settings that around a year ago gave the best
> balance between crashes and halts from the garbage collector.
> But are these settings optimal for Tomcat 6 and Java6?

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