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From Leon Rosenberg <>
Subject Re: Tomcat 100% CPU usage after moving from Java 5 to 6
Date Tue, 26 Jan 2010 17:44:45 GMT
On Tue, Jan 26, 2010 at 4:50 PM, Jesse Klaasse <> wrote:
> Hi Chuck, thanks for your extensive comments about the JVM options..

On a site note... I have made the observation that the JVM is
performing best without any explicit gc settings. Most time explicit
GC settings just cause havoc (fixes sized generation spaces lead to
100% cpu usage and continuous full gcs, some performance options are
extremely vm version specific and so on).

Among the sites of my customers, one site is serving more than 500
requests per second in a single tomcat with only following options:
-Xmx16G -Xms16G -XX:MaxPermSize=512M -XX:+PrintGCDetails -XX:+PrintGCTimeStamps

Another customer of mine was playing with gc settings for nearly a
year, because his tomcats collection times went higher and higher, and
after a short look at the heap dump with jmap and jhat, we found out
that he had 100.000.000 uncollectable garbage objects in the heap (2/3
of his heap actually). Instead of investigating his heap pollution he
spent 11 month playing with gc options to setup a faster gc. In the
end the problem was solved in two days.

Most time I've seen people playing with gc settings, nothing good came
out of it, save for real experts like Chuck.
Thats just a side note ;-)


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