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From David Wall <d.w...@computer.org>
Subject Re: Java/Tomcat 5 CPU utilization very high under low load
Date Wed, 28 Jan 2009 19:19:31 GMT

> F.ex. from my toy machine;
> $ ps -fLp 7044
> UID        PID  PPID   LWP  C NLWP STIME TTY          TIME CMD
> tomcat    7044     1  7044  0   40  2008 ?        00:00:12 /usr/lib/jvm/java/bin
> tomcat    7044     1  7118  0   40  2008 ?        00:02:58 /usr/lib/jvm/java/bin
> tomcat    7044     1  7119  0   40  2008 ?        00:00:00 /usr/lib/jvm/java/bin
> ...
> tomcat    7044     1  7892  0   40  2008 ?        00:36:26 /usr/lib/jvm/java/bin
> ... (there are a number of other threads)
>
> Then, at least on my JVM, the thread ids are shown in hexadecimal, so
> it's best to convert the "interesting" thread ids to hex; from the above,
> 7044=0x1b84
> 7118=0x1bce
> 7119=0x1bcf
> 7892=0x1ed4
>
> ... and the thread info from the dump matchind to the above:
> "main" prio=1 tid=0x0805cfb8 nid=0x1b84 runnable [0xbfffc000..0xbfffd708]
> "VM Thread" prio=1 tid=0x08099f38 nid=0x1bce runnable
> "Reference Handler" daemon prio=1 tid=0x0809cae0 nid=0x1bcf in Object.wait() [0xb2519000..0xb2519f20]
> "ContainerBackgroundProcessor[StandardEngine[Catalina]]" daemon prio=1 tid=0x083444e0
nid=0x1ed4 waiting on condition [0xb135c000..0xb135cfa0]
>
> In the dump there is also the call stack for each of the threads,
> so if it's an application thread that's using CPU, you'll get at least
> some glimpse where in the code the time is spent.
>   

Thanks for the detailed explanation, Juha.  When I get some info, I'll 
post back what I find.  I've added your 'ps' commands to our checking, 
along with the jmap and thread dumps suggested as well.   Hopefully 
we'll be able to find it.

I was interested to see that it could also be SOAP threads that get in 
trouble, since another aspect of this particular deployment is that it 
uses the Salesforce SOAP APIs to update data back in Salesforce, so 
perhaps it will be something there. 

David


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