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From Vassil Dichev <vdic...@apache.org>
Subject Re: Memory usage -> stability probs?
Date Tue, 23 Jun 2009 06:46:25 GMT
> I added code that will dump memory information every 10 minutes.  Please put
> the new code live.  If it barfs, please send me the output (privately is
> better so we don't spam the list with a 10MB file)
> I'm running an instance on my local box and will see if I can find memory
> leaks.

This is cool, but I'm afraid we might need some extra info from the
JVM. I'm not sure you can change the command-line or environment you
use to start the application in Stax, but this should display detailed
information for the Sun JVM.

MAVEN_OPTS=-verbose:gc -XX:+PrintGCDetails -XX:+PrintClassHistogram

and for extra debugging, you can turn on the built in profiler with
the following options:

-Xrunhprof:heap=sites,cpu=samples,doe=y

It will make the JVM run even slower, but could really pinpoint where
the problem was.

As for thread dumps, they're even more useful if you encounter the
100% CPU issue, but we need to send a signal to the JVM, which I'm not
sure you can do at all in a managed stax environment. There are
solutions to trigger it programmatically, but you need to include a
native library, which is another restriction we might not be able to
overcome.

All in all, it would be much better if we can reproduce it locally,
where we can play with the application. I assume you couldn't set
MAVEN_OPTS last time there was a problem, since there was no feedback.
Monitoring an app for memory problems in a restricted environment is
notoriously hard.

Vassil

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