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From Mark Thomas <>
Subject Re: Headstart on "Resolving OOM-PermGen errors on webapp reload"
Date Tue, 21 Apr 2009 21:54:58 GMT
Ken Bowen wrote:
> Mark,
> Any chance we could make a headstart on "Resolving OOM-PermGen errors on
> webapp reload" ??
> Perhaps some general pointers, guidance etc. [to help you refine the
> talk in advance :-) ]

The very short version.

1. Find an app that you can't reload without OOME
2. Get a profiler - I like Yourkit
   Full disclosure: they give ASF committers a free copy
3. Reload you app once
4. Use the profiler to look for instances of WebappClassLoader
5. Look for the one with the started attribute == false
6. Trace the GC roots for this instance
7. Fix whatever is hanging on to references to the instance - there
should not be any

The session (assuming it goes ahead) will do a demo of the above and
expand on 7 in terms of typical culprits and possible workarounds. It
will also explain what is going on and why this happens.



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