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From Martin Gainty <mgai...@hotmail.com>
Subject RE: Tomcat Memory and Garbage Collection questions...
Date Fri, 06 Nov 2009 00:54:57 GMT

you're going to want to trap the stack and heap parameters with all the tools chuck mentioned
you're going to want to note which webapps are being loaded and where (do you have a cluster)
track ALL the resource changes you make specifically Database resources which can consume
unrestricted heap as well any any file i/o or graphic packages loaded

in the end run heap space not being reclaimed can be caused by a thousand different things

we can provide a comprehensive solution if we would be able to submit bids for a statement
of work where one of us will come down and take a look

thanks,
Martin Gainty 
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> From: Trevin.Johnson@occ.treas.gov
> To: users@tomcat.apache.org
> Date: Thu, 5 Nov 2009 17:26:14 -0500
> Subject: RE: Tomcat Memory and Garbage Collection questions...
> 
> I see odd behavior. Our tomcat setting is set for a max memory setting of 256Mb in our
Development Environment. Yet it goes over 256Mb. Up to 290Mb. I assumed that it would never
go over 256Mb in task manager. Is that correct?
> thanks
> 
> Answers Below as well... 
> 
> -----Original Message-----
> From: Caldarale, Charles R [mailto:Chuck.Caldarale@unisys.com] 
> Sent: Monday, November 02, 2009 4:06 PM
> To: Tomcat Users List
> Subject: RE: Tomcat Memory and Garbage Collection questions...
> 
> > From: Johnson, Trevin (Contractor)
> > [mailto:Trevin.Johnson@occ.treas.gov]
> > Subject: Tomcat Memory and Garbage Collection questions...
> > 
> > When we restart the tomcat service our tomcat memory is about 120Mb. It
> > keeps going up over the next few days util it reaches 700Mb and we have
> > to reboot the server.
> 
> Why do you reboot?  Is the server unresponsive?
> -We actually just restart Tomcat service and it goes back down to about 120Mb
> 
> > 1.We do not see the memory going down for the tomcat service. Shouldn't
> > the memory go down as well as up over this timespan
> 
> What are you using to show the memory usage?
> -We are using task manager to show Tomcat memory usage
> 
> > 2.Should the memory get to maximum 768Mb and then go back down or get
> > recycled?
> 
> Depends on what you're looking at.  If it's Task Manager, it won't go down.  If you're
using JConsole to look at the heap, it should go up and down.
> 
> > 3.Is this a bug or what is normal behavior for the tomcat memory?
> 
> Depends; see above.
> 
> > 4.. How do we implement garbage collection for our windows server(-
> > Xincgc)?
> 
> Garbage collection is always present.  Incremental GC can be useful to minimize pause
times, but it is more overhead and has some restrictions on just what it can collect.  Unless
you really think you need that option, I wouldn't set it right now.
> 
> I'd strongly recommend using JConsole to look at heap usage, then use a profiler if you
find that the heap usage does not stabilize.  You can also turn on -verbose:gc, and use jhat
and jmap to do basic heap analysis.
> 
> Some useful resources:
> http://java.sun.com/j2se/1.5.0/docs/guide/vm/gc-ergonomics.html
> http://java.sun.com/javase/technologies/hotspot/gc/index.jsp
> 
>  - Chuck
> 
> 
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