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From Kevan Miller <kevan.mil...@gmail.com>
Subject Re: Geronimo v2.1 Plan Creator => Deploy Liferay 4.1.1
Date Thu, 06 Mar 2008 16:52:25 GMT

On Mar 6, 2008, at 10:37 AM, Jim Foster wrote:

>
> Hi Peter,
>
> Thank you for this info!
>
> I took your suggestion and brought myself up to speed on PermGen,  
> and a good
> bit of all things related to Java.lang.OutOfMemoryError.
>
> All I can say is that there's certainly a lot more to fine-tuning the
> classloading going on behind the scenes than one would first imagine.
>
> This brings up another question: How do you folks manage this?
>
> What tools would you recommend that I add to my toolbox so that I  
> can really
> understand what's really going on beneath the covers?
>
> As I mentioned in my earlier post, this project I am involved with  
> will be
> weaving together several applications to be deployed on top of  
> Geronimo, so
> sooner or later, fine-tuning performance issues will become a reality.
>
> I'd like to get a handle on such things as early in the development  
> cycle as
> possible.

Hi Jim,
There are a lot of knobs and switches. However, you can cause as much  
harm as good trying to fine tune their settings. My advice to you is  
to keep things as simple as possible until you know you have a problem.

The JVM can print GC statistics to STDOUT. Often I find this  
sufficient for getting a broad overview of what's going on. You can  
also configure the JVM to create a heapdump on OOME conditions. If you  
have a memory leak, you can then analyze the heapdump using a variety  
of tools (I like YourKit). There are a number of tools which can also  
perform further analysis on runtime data (memory allocations, method  
execution, etc).

Something like the following should work  (set max heap and max perm  
to suit your environment):

-Xmx512m -XX:MaxPermSize=128m -verbose:gc -XX:+PrintGCDetails -XX: 
+HeapDumpOnOutOfMemoryError

--kevan

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