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From Philippe Deslauriers <>
Subject Why is tomcat (java) so memory intensive?
Date Tue, 21 Dec 2004 14:53:22 GMT

I am using Tomcat 5.0.19 on Windows XP SP2, J2SDK 1.4.2_03.

I have a serious memory problem with Tomcat, it just EAT memory without
explanation, until OOM error occurs.

The Java.exe process in the windows task manager reports using between 95Mb
and 105Mb after the startup of the webapp. I do not use Xms Xmx options in
dev mode. It just grows until it runs out of memory. There is not much
memory available (around 150Mb), yet it should be enough for a few classes,
JSP and almost not data in the database.

Like a big boy, I decided to use Jprofiler demo to figure out where the
memory leak was, to see that there is only 20 Mb allocated by the VM!!! So
where does the rest of the memory goes? I do not use any non-java library
(dll), I don't think I'm doing anything special.

The app use a the Versant JDO implementation (instead of direct JDBC) using
MS SQL server. But hey, the app is still in dev mode, with only the
developpers using it, the DB is (almost) empty, so the amount data is not in
cause. Anyways using 20Mb of heap is very reasonable (there will be at least
1gb available in production), but why is the java.exe process eating memory
like a pig an the profiler is not showing where the mem goes? (by the way, I
did deleted ALL the filters from Jprofiler). If the app would take 2Gb in
memory I would not care, as long as I know what is using the memory.

I did profile an app running on 5.0.18, and the same magic happens, the
memory used by the java.exe is far from close to what the total heap size of
the VM reports to be.

Am I going crazy?

Any ideas?



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