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From "Caldarale, Charles R" <Chuck.Caldar...@unisys.com>
Subject RE: Monitoring Tomcat with Jconsole
Date Mon, 24 Nov 2008 22:18:24 GMT
> From: André Warnier [mailto:aw@ice-sa.com]
> Subject: Re: Monitoring Tomcat with Jconsole
>
> I don't know if the jconsole offers a cleaner way of doing this

I'm not aware of any mechanism in JConsole to send the output anywhere, other than via the
clipboard.

> After this processing, the process in a "top" display shows
> the following :
> 22175 star      21   0  266m  23m  11m S  1.0  4.6   0:14.61 java
> (where 266m is the virtual memory, and 11m the resident one).

The top virtual number is just what's in the memory map for the process, so that includes
files, code, non-Java stuff, etc., as well as the JVM heap.  The resident memory number is
the pages that happen to be in RAM at the moment.

> Compared to the numbers I see in the jconsole VM summary below,
> these memory figures seem to show a gross disproportion, or am I
> interpreting this wrong ?

> Snapshot 1
> Current heap size:
>    785 kbytes

This is just the combined virtual size of the new and old generations; it does not include
PermGen.

> Maximum heap size:
> 65.088 kbytes

How big the new + old can get, if needed.

> Committed memory:
> 1.984 kbytes

Includes the JIT's code pool, C heap, Java heap, PermGen, and various other bits and pieces
the JVM knows about.

> Committed virtual memory:
> 270.980 kbytes
> Total physical memory:
>   516.920 kbytes
> Free physical memory:
>     6.852 kbytes
> Total swap space:
> 1.297.564 kbytes
> Free swap space:
> 1.234.376 kbytes

All of the above are for the entire system, not just this one process.

> Snapshot 2
> Current heap size:
>  1.828 kbytes

The heap has expanded a bit.

> Maximum heap size:
> 65.088 kbytes

This can't change.

> Committed memory:
> 2.452 kbytes

Increased due to heap expansion plus probable enlarging of the code pool, C heap, PermGen,
etc.

Nothing unexpected here.

 - Chuck


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