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From "Kevin Williams" <KWilli...@centerlogic.com>
Subject RE: tomcat CPU utilization pegged...total CPU only 50%
Date Tue, 08 Feb 2005 21:15:41 GMT


> -----Original Message-----
> From: Caldarale, Charles R [mailto:Chuck.Caldarale@unisys.com]
> Sent: Monday, February 07, 2005 10:04 PM
> To: Tomcat Users List
> Subject: RE: tomcat CPU utilization pegged...total CPU only 50%
> [bcc][faked-from][bayes]
> Importance: Low
> 
> > From: Kevin Williams [mailto:KWilliams@centerlogic.com]
> > Subject: RE: tomcat CPU utilization pegged...total CPU only 50%
> >
> > The two Xeon CPU's are hyperthreaded to represent 4 CPU's
> > on the machine.  I'm not sure exactly how tomcat/java
> > interact with this, but it was not favorable.
> 
> Other than for determining the number of threads to use for parallel
GC,
> the JVM does not care how many CPUs there are.  I don't know what
Windows
> returns for the number of CPUs installed when hyperthreading is
enabled,
> but you can determine that with the Runtime.availableProcessors()
method.
> 
> You really should be measuring performance by some measurement of
actual
> workload completed, not CPU utilization.  Turning off hyperthreading
may
> actually reduce your overall throughput.  (Then again, it might make
it
> better - very application dependent.)
> 
> 

You're right.  I was measuring average response time.  The CPU was just
the bottleneck.  My average response time under a specified user load
actually decreased with hyperthreading off.  My next step is to start
analyzing the code:)

Thanks for the pointer!

Kevin Williams

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