Re: 2.6 vs 2.4 regression when running gnomemeeting

[Christian Meder]

On Sat, 2003-12-20 at 01:48, Nick Piggin wrote:
> 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

Ok. I've attached the logs from a run with a call with only an
additional dd. The quality was almost undisturbed only very slightly
worse than the unloaded case.

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

Worse than unloaded and worse than the disk loaded case from above. But
all (CPU) loaded cases were producing almost complete audio dropouts
while with your scheduler and renicing to -10 I got at least a
stuttering audio stream (a regular pattern of very short slices of audio
mixed with very short slices of silence).

> whats your /proc/cpuinfo?

processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 8
model name      : Pentium III (Coppermine)
stepping        : 1
cpu MHz         : 451.193
cache size      : 256 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca
cmov pat pse36 mmx fxsr sse
bogomips        : 447.48



				Christian Meder

-- 
Christian Meder, email: chris@xxxxxxxxxxxxxxx
 
What's the railroad to me ?
I never go to see
Where it ends.
It fills a few hollows,
And makes banks for the swallows, 
It sets the sand a-blowing,
And the blackberries a-growing.
                      (Henry David Thoreau)

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