Subject: What do I do with a heap dump? (OOM Permgen) 2007-11-01 - By Greg Vilardi
Back
Hello everyone.
My team and I are trying to develop a new web application and the
tomcat JVM is crashing every few days. We are deploying our separate
versions of the application several times per hour, and by looking at
jprobe, I see that each deployment of a webapp consumes 440kb of
PermGen space. This space does not seem to be released, although I've
only been monitoring this for 4 hours now. I have a heap dump from the
last crash, (courtesy of +XXHeapDumpOnOutOfMemoryError) and have taken
two memory dumps using jmap before and after a redeploy on an otherwise
quiescent JVM.
Now, having done this, I've also looked at the dumps using jhat. There
seems to be a vast amount of data there, but I can't distill the
information I need out of it. I apologize if my Google-Fu is weak, but
I didn't find much real information on interpreting jhat data.
Preliminary examination of the jhat data does not show much of my
application or helper classes (mysql, jdbc).
So, my questions are:
How do I figure out what is in that 440kb per deployment?
Is there an FM for me to R on how to interpret jhat data?
What should I be looking for?
How do I break this problem down further?
The environment is:
OS: Debian etch 2.6.21 kernel
JVM: Sun Java 6 1.6.0-b105 Configured for use with jprobe and default
memory allocations. (This was done to try to make the problem easier to
reproduce/study.)
Tomcat: 6.0.14 fronted via Apache 2.2.4 using mod_proxy_ajp.
Database: MySQL 5.0.32 using the latest ConnectorJ.
The application is a combination of JSP and servlets with some AJAX but
no Comet, Hibernate, &c. Apache and Tomcat were hand installed (not
from Debian packages).
Any help that you can provide would be greatly appreciated.
-Greg
--
Gregory H. Vilardi 631-752-2701x240 gvilardi@(protected)
Project Manager / Lead Software Engineer Fax: (631)752-3397
Recurrent Software Solutions, Inc. http://www.recurrentsoft.com
1 Huntington Quadrangle, Suite 1C02, Melville, NY 11747
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