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From Kevan Miller <kevan.mil...@gmail.com>
Subject Re: Geronimo v2.1 Plan Creator => Deploy Liferay 4.1.1
Date Sat, 08 Mar 2008 12:49:50 GMT

On Mar 7, 2008, at 12:12 PM, Jim Foster wrote:

>>
>> 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.
>>
>
>
> Hi Kevan,
>
> Simple is good.
>
> I will certainly take your advice. I just know from experience that  
> it best
> to put a lasso around potential system-related problems like this  
> early in
> the game...if not they may assume an exponential flight path.

Understood. IMO, this is a like optimizing code execution. Spend some  
time with algorithmic analysis, but don't spend too much time trying  
to optimize arbitrary code paths. Wait until you have actual  
performance data that indicates where you will get the most bang for  
your buck. Measure, then optimize.

You may find the following blog useful -- http://kirk.blog-city.com/advice_on_jvm_heap_tuning_dont_touch_that_dial.htm

>
>
>
>
> Kevan Miller wrote:
>>
>> 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
>>
>>
>
>
> This is good to know.
>
> It's probably too early for me to be thinking of dropping $500 for a
> profiler like YourKit, but just leveraging the command line options  
> as you
> suggest should help in keeping things from getting out of control.
>
> I appreciate your sharing this.  Thanks!

Heh.

/me confesses that I use YourKit under an Open Source license (e.g.  
free). I also mainly use it for memory leak diagnosis...

There are free tools that will analyze the GC statistics. However, I  
generally just eyeball things until I'm really getting serious about  
tuning... HPjtune is pretty good -- http://www.hp.com/products1/unix/java/java2/hpjtune/

--kevan

--kevan

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