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From Martin Gainty <mgai...@hotmail.com>
Subject RE: CPU utilization and Tomcat 5.5.20
Date Sat, 04 Oct 2008 00:30:03 GMT

yes pls follow leon's advice and compare your thread dumps so you can determine TC thread
activity
and coordinate that to the webapp's resource activity

I would look at minHeap, maxHeap and stack parameters from %JAVA_OPTS%
a 2004 post http://forums.sun.com/thread.jspa?messageID=10055131 says it best



The default stack size is 256K on UNIX and on 32-bit Windows operating systems. To set Stack
size

java -XX:NewSize=128m -XX:MaxNewSize=128m -XX:SurvivorRatio=8  -Xms512m -Xmx512m



1. Setting the New generation heap size

 -XX:NewSize
 Use
this option to set the New generation Java heap size. Set this value to
a multiple of 1024 that is greater than 1MB. As a general rule, set
-XX:NewSize to be one-fourth the size of the maximum heap size.
Increase the value of this option for larger numbers of short-lived
objects.



Be sure to increase the New generation as you increase the number of
processors. Memory allocation can be parallel, but garbage collection
is not parallel.

 

2. Setting the maximum New generation heap size

 -XX:MaxNewSize

Use this option to set the maximum New generation Java heap size. Set
this value to a multiple of 1024 that is greater than 1MB.

 

3. Setting New heap size ratios

 -XX:SurvivorRatio

 The New generation area is divided into three sub-areas: Eden, and two survivor spaces that
are equal in size. 



Use the -XX:SurvivorRatio=X option to configure the ratio of the
Eden/survivor space size. Try setting this value to 8, and then monitor
your garbage collection.

 

4. Setting minimum heap size

 -Xms

Use this option to set the minimum size of the memory allocation pool.
Set this value to a multiple of 1024 that is greater than 1MB. As a
general rule, set minimum heap size (-Xms) equal to the maximum heap
size (-Xmx) to minimize garbage collections.

 

5. Setting maximum heap size

 -Xmx

 Use this option to set the maximum Java heap size. Set this value to a multiple of 1024 that
is greater than 1MB.



 




    


    


pay attention to MaxHeap, MinHeap, StackSize and set your GC's to mark and sweep for discarded
blocks

HTH
Martin Gainty 
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> Subject: CPU utilization and Tomcat 5.5.20
> Date: Fri, 3 Oct 2008 14:29:23 -0500
> From: reistom@cod.edu
> To: users@tomcat.apache.org
> 
> We are running Tomcat 5.5.20 with jvm 1.5.0_14. Tomcat utilization goes
> to 100 percent being used by Tomcat. Any ideas why the utilization would
> go so high. Thanks. 

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