6.1 responsiveness under heavy (cpu?) load + thread monitoring

[Mathieu Prevot]

On Sat, Apr 01, 2006 at 01:07:42PM -0800, Kevin Oberman wrote:
> > Date: Sat, 1 Apr 2006 16:34:25 +0200
> > From: Mathieu Prevot <freebsd-stable at club-internet.fr>
> > Sender: owner-freebsd-stable at freebsd.org
> > 
> > Hello,
> > 
> > I have a RELENG_6/AMD64 with an AMD64X2 cpu, 1GB of memory, 512MB swap.
> > I remarked that when I run 2 simulation program [1], sometimes, one of them
> > run one or several of its threads [2] very slowly, but sometimes, it doesn't
> > occur.
> > 
> > I remarked that is doesn't depend on SMP/UP, ULE/4BSD, i386/AMD64.
> > 
> > It seems to occur also with the kernel stress test under the same conditions
> > (all of them).
> > In this case, the mouse is blocked, etc. I tested different kernels, and
> > recorded the output of sysctl vm [3].
> > 
> > I increased vm.swap_async_max but this doesn't change the deal /a priori/.
> > 
> > All that didn't occur with a Sempron64. All was slower but the mouse didn't
> > blocked etc. This was a time ago, I may be wrong.
> > 
> > It seems to be an architecture problem (??).
> > I can give more quantitative data, but I need help to focus the tests...
> > 
> > Mathieu
> > 
> > [1] http://ising.podzone.org/src/ising_lps_0.4.tar.bz2
> > [2] void *interface(void *arg) can be very slow, void *system_trace(void *arg)
> >  can exit during a very long time (terminated ? detached: it should).
> > [3] http://ising.podzone.org/vm/vm_amd64.tar.bz2 and others in this directory
> 
> Mathieu,
> 
> Any chance your system was running tight on memory? How much does it
> have and is the system using any swap space?
I have 2x 512MB DDR 400Mhz. And the simulation program doesn't use much memory
(around 20MB, depending on initial conditions).
I didn't check if swap was used. I guess it's not the case because the hard
drive is not used during calculation.


> I suspect that something is not working well in V5 or V6 with writing
> to/reading from swap. I have reported a similar problem and Kris
> K. asked me to try adjusting vm.swap_async_max, but the system has been
> replaced and I ave been having trouble getting a systems set up to
> test. (Disk died.) I hope to try Kris's suggestion next week, but your
> report makes this seem less likely.
But my report is qualitative, not quantitative. I should do a reproductible test
with measures. I need help/programs for a real investigation.


> I can say that I don't see this on my new system which increased memory
> from 256MB to 1GB. Needless to say, it seldom has to use the swap file
> and I must agree that it seems tied to threaded processes.
Yes. The situation is not always reproductible, the big slow down doesn't always
occur.

I will try solaris and thr instead of pthread.

Mathieu

> -- 
> R. Kevin Oberman, Network Engineer
> Energy Sciences Network (ESnet)
> Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
> E-mail: oberman at es.net			Phone: +1 510 486-8634
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