Re: 2.6.12 Performance problems

Denis Vlasenko
2005-08-22T22:11:51Z

On Sunday 21 August 2005 23:21, Danial Thom wrote:
> > You problem could very well be something else
> > entirely, but try a
> > kernel build with PREEMPT_NONE and HZ=100 and
> > see if it makes a big
> > difference (or if that's your current config,
> > then try the opposite,
> > HZ=1000 and PREEMPT). If it does make a
> > difference, then that's a
> > valuable piece of information to report on the
> > list. If it turns out
> > it makes next to no difference at all, then
> > that as well is relevant
> > information as then people will know that HZ &
> > preempt is not the
> > cause and can focus on finding the problem
> > elsewhere.
>
> Yes. Hz isn't going to make much difference on a
> 2.0Ghz opteron, but I can see how premption can
> cause packet loss. Shouldn't packet processing be
> the highest priority process? It seems pointless
> to "keep the audio buffers full" if you're
> dropping packets as a result.
>
> Also some clown typing on the keyboard shouldn't
> cause packet loss. Trading network integrity for
> snappy responsiveness is a bad trade.

You do not need to argue about usefulness of preempt
(or lack thereof). You need to try non-PREEMPT kernel
as suggested (if you really are interested in fixing
performance degradation you observe, that is).

http://www.catb.org/~esr/faqs/smart-questions.html
--
vda