Re: how to tell what's using memory?

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Excellent. 

This does, in fact, appear to be how it's working. I rebooted the
machine, without starting the oc4j application and took note of the
memory usage numbers. then I started oc4j and took note of the change in
the numbers. Then, I stopped the app and looked at the numbers again.

The amount of memory "released" by stopping the application, was indeed,
not as much as you would expect under the "Microsoft" model. In fact,
very little memory was released.

On a related note, do you happen to know of any software that analyzes
the memory footprint of the system and provides a nice, easy to
understand description of how that memory is divided up according to the
various applications?

mike

On Mon, 2003-08-18 at 12:21, Jesse Keating wrote:
> On Monday 18 August 2003 09:14, Michael Martinez wrote:
> > We've got a RH Linux ES 2.1 server (Redhat 7.2 smp) that has 3.5 Gig
> > on board memory.
> >
> > We've got minimal processes running on this thing. Usually about 3.0
> > Gig RAM is free.
> >
> > however, we have an oc4j (java) application that uses up a small
> > amount of memory, probably about 100Meg.
> >
> > Applications folks were stress testing this application over the
> > weekend, and noticed that the application was using up memory. Then,
> > they shut down the application, but the memory was not freed.
> >
> > Now we're trying to figure out why the memory was not freed. none of
> > the application threads are showing up in the "ps" output, but the
> > memory usage for the total system is at about 1.7Gig usage, with 1.8
> > Gig free.
> >
> > We expect there should be almost 3 Gig free. So how do we find out
> > what's holding the rest of the mem?
> 
> In the world of Unix, unused ram is wasted ram.  You're seeing buffering 
> and caching in action.  Take a closer look at "free -m" and you'll see 
> the difference line (+/- buffers/cache).  When you think about it, 
> Microsoft's model of use as little physical ram as possible, and as 
> much page file as possible, thus showing a huge amount of "free ram" is 
> really quite silly and wastefull.  The "in use" ram of your Linux 
> system will be freed as needed, but next time you run that particular 
> app, it'll run much faster due to all of it's info being cached.
> 
> -- 
> Jesse Keating RHCE MCSE
> http://geek.j2solutions.net
> Mondo DevTeam (http://www.microwerks.net/~hugo/)
> 
> Was I helpful?  Let others know:
>  http://svcs.affero.net/rm.php?r=jkeating
> 
> 
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-- 
Michael Martinez
Linux System Administrator
ISTM/CSREES/USDA


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