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From Aditya <>
Subject Re: tracking memory usage over time
Date Wed, 26 Feb 2003 01:25:26 GMT

several months ago you had posted a URL to a document (at if I remember correctly) where you talked about
having to restart your production Tomcat(s) every 4 weeks or so due to
Heap exhaustion. Is that still the case? If so what causes the heap

We've looked high and low, with JProbe etc, and we still can't find
where the "leak" is. We're having to restart a Tomcat (4.1.20) with
-Xms and -Xmx both set to 256M every 4 days or so.


> On Fri, 14 Feb 2003 06:45:26 -0600, Glenn Nielsen <> said:
> An easier way to measure memory usage in production is to start the
> JVM which runs Tomcat with the arg -verbose:gc, this will print
> information to stdout about each garbage collection and the memory
> used.

> I doubt if the memory leak is in Tomcat itself.  The best way to
> find the memory leak in your application is to setup a test server
> and use OptimizeIt or JProbe to profile Tomcat and your web
> application.  You can use something like JMeter to simulate load.

> Regards,

> Glenn

> Aditya wrote: I have the following JSP that I hit every 5 minutes
> and stuff the returned values into a RRD ( to
> measure the memory (heap I presume) consumption of Tomcat over
> time. Is there a "better" way, short of using JMX in the newer
> Tomcat builds, of doing this?  <%@ page language="java" %> <%@ page
> session="false" %> <% long free =
> java.lang.Runtime.getRuntime().freeMemory(); long total =
> java.lang.Runtime.getRuntime().totalMemory(); out.print(free + "|" +
> total + "|"); %> I can see a clear leak (about 20 contexts with a
> dozen or so hit constantly and recompiling JSPs very often) which
> necessitates (-Xmx and -Xms set to 256 MB) a restart of Tomcat every
> 4 days or so (with 4.1.14). I just upgraded to 4.1.20 thinking that
> the constant compiling was the source of the leak and that doesn't
> seem to have made a difference. Running 4.1.14 under jprobe doesn't
> evidence any leaks in our JSPs/filters.  Hints on how to trace this
> leak down would be most welcome.  Thanks, Adi
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