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From "Leon Rosenberg" <>
Subject Re: Tomcat not using multiple cores
Date Thu, 16 Oct 2008 22:03:41 GMT
Hello Matthew,

Without wanting to advertise own product, I think moskito can help you
a lot here. It was specially designed to detect
cpu eaters among call trees. Feel free to contact me of list if you
want to give it a try ;-)


On Thu, Oct 16, 2008 at 10:30 PM, Matthew Laird <> wrote:
> We're pulling our hair out with a Tomcat issue.
> We have an in-house application running on Tomcat 5.5 with Sun JDK 1.6.
>  The machine is an x86 dual-CPU, quad core (8 cores total) with 16GB of
> RAM.  We're running OpenSuSE 10.2, 32-bit.  Java memory size set to 2GB,
> multi-threaded GC enabled.
> What occurs is when a user clicks a certain kind of analysis on the
> website, data is retrieved from a database and then a lot of formatting
> is done before returning it to the user.  This typically causes 100% CPU
> usage for this thread for a few minutes (bioinformatics application,
> that part isn't going to change).
> Unfortunately what then occurs is all other threads suddenly become
> unusably slow.  The entire web application grinds to a halt until this
> thread that's running hot completes.
> Looking at top, it appears that these threads aren't spreading among all
> the cores.  I see one core go to 100% usage, and the others stay at 100%
> idle.  So we're running multi-thread, but because everything is staying
> on the same core, we're still getting thread contention that's bringing
> the entire application to its knees.
> The only time I began to see the other cores actually start being used
> is when I enabled multi-threaded GC.  But that doesn't give much
> improvement since the threads responding the web requests are still all
> on the same core.
> I'm not sure how to convince the Tomcat/Java container to spread its
> threads among the cores.
> Thanks.
> --
> Matthew Laird
> Lead Software Developer, Bioinformatics
> Brinkman Laboratory, MBB Dept.
> Simon Fraser University
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