Re: 2.6 vs 2.4 regression when running gnomemeeting

[Nick Piggin]

Christian Meder wrote:

> On Sat, 2003-12-20 at 01:21, Nick Piggin wrote:
>
> > Christian Meder wrote:
> >
> >
> > > On Fri, 2003-12-19 at 21:32, William Lee Irwin III wrote:
> > >
> > >
> > > > On Fri, Dec 19, 2003 at 09:11:50PM +0100, Christian Meder wrote:
> > > >
> > > >
> > > > > I've got a longstanding regression in gnomemeeting usage when switching
> > > > > between 2.4 and 2.6 kernels.
> > > > > Phenomenon: 
> > > > > Without load gnomemeeting VOIP connections are fine. As soon as some
> > > > > load like a kernel compile is put on the laptop the gnomemeeting audio
> > > > > stream is cut to pieces and gets unintelligible . On 2.4.2x I don't get
> > > > > even the slightest distortion in the audio stream under load. I played
> > > > > around with different nice levels with no success. The problem persisted
> > > > > during the whole 2.6.0-test series no matter whether I used -mm kernels
> > > > > or pristine Linus kernels. Even when nicing the kernel compile to +19
> > > > > the distortions start right away. I tried Nick Piggin's scheduler which
> > > > > fared slightly better after changing the nice level of gnomemeeting to
> > > > > -10 but it's still a far cry from the 2.4.2x feeling without any
> > > > > fiddling with nice values.
> > > > > Any hints where to start looking are greatly appreciated.
> > > > Please instrument your workload with the following, and send logs of the
> > > > output (preferably compressed) to me and possibly others:
> > > >
> > > > top b d 5
> > > > vmstat 5
> > > > while true; do cat /proc/vmstat; sleep 5; done
> > > > while true; do cat /proc/meminfo; sleep 5; done
> > > >
> > > > A good way to log commands like this is:
> > > >
> > > > (command) > /home/foo.log.1 2>&1 &
> > > >
> > > > where parentheses surround the command in the actual shell input.
> > > Hi,
> > >
> > > I've attached the tarred output of a gnomemeeting run without load and
> > > without distortions and another tarred output of a gnomemeeting run
> > > while compiling a kernel with severe distortions in the audio stream.
> > You're getting a lot fewer interrupts in the loaded case. Maybe its
> > the sound card driver that has the regression from 2.4? It could be
> > that 2.6 allows a smaller sound fragment size which is more stressful.
>
> Well I had the same problem with the OSS driver on 2.6. Now I use the
> ALSA driver because I thought that could possibly improve things. The
> ALSA driver is better indeed but it doesn't change this particular
> phenomenon. Additionally I'd guess that the latest ALSA driver in 2.4
> and 2.6 doesn't differ significantly and 2.4.2x with the latest ALSA
> works great while 2.6 doesn't.

Sounds reasonable. Maybe its large interrupt or scheduling latency
caused somewhere else. Does disk activity alone cause a problem?
find / -type f | xargs cat > /dev/null
how about
dd if=/dev/zero of=./deleteme bs=1M count=256

You said it faired slightly better with my scheduler when renicing
gnome meeting to -10. How much better is that?

whats your /proc/cpuinfo?


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