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From Hüsnü Þentürk <husnusent...@yahoo.com>
Subject Re: tomcat memory usage
Date Fri, 29 Jan 2010 14:11:38 GMT
Chuck and Chris,
Thanks for yor explanations,

Let me, try to summarize what I understand  adding some extra info and ask my questions.

Is following classifications true for memory usage of Java ? If not please correct it.

A. Java memory usage when application is started as a windows service:
	1. Heap memory
	* objects
	2. Non-heap memory
	* PermGen (holds reflective data (meta-data) of the JVM itself, such as class and method
objects and static fields )
	* JVM's itself ( Garbage collector, managing heap etc.)
	* Java service wrapper dlls.
  
B. Java memory usage when application is with a batch file:
	1. Heap memory
	* objects
	2. Non-heap memory
	* PermGen (holds reflective data (meta-data) of the JVM itself, such as class and method
objects and static fields )
	* JVM's itself ( Garbage collector, managing heap etc.)
________________________________

If I turn my first e-mail, in my example, java heap size was 512 MB, I did'nt define  PermSize
parameter so application uses default value 64 MB. Sum of PermGen and Heap memory usage smalller
then 600,980 KB which I see on Task Manager. Can you explain the reason of this difference?

 
 Heap             PermGen                      
512 MB    +   64 MB    = 576 MB = 589824 KB <   600980 KB
 
Firs e-mail
"In our company, we are using apache tomcat as a windows service. We defined jvm parameters
"--JvmMs 512 --JvmMx 512" in service.bat. But application is using 600,980 KB memory. I expect
the application not to use more then 512 MB. "
 
 
Thanks again.

 



________________________________
From: "Caldarale, Charles R" <Chuck.Caldarale@unisys.com>
To: Tomcat Users List <users@tomcat.apache.org>
Sent: Wed, January 27, 2010 10:32:01 PM
Subject: RE: tomcat memory usage

> From: Christopher Schultz [mailto:chris@christopherschultz.net]
> Subject: Re: tomcat memory usage
> 
> What else goes into PermGen, other than java.lang.Class objects?

It varies by JVM level.  In the original HotSpot implementation it was pretty much just the
instances of java.lang.Class.  As things evolved, a lot of class/method/field metadata migrated
into PermGen from the C heap, pushed there, I suspect, by the growing use and sophistication
of JMX and JVMTI, as well as making it easier for GC to clean up dead classes.  AFAIK, none
of these secondary structures are directly visible to Java code.

- Chuck


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