Re: [PATCH] sched: Improve latencies under load by decreasing minimum

Re: [PATCH] sched: Improve latencies under load by decreasing minimum

[Matthias Dahl]

Hi.

I don't know if this is relevant but I just tried this ontop 2.6.35.4 while
investigating a different problem and it was quite easy to produce audio
buffer underruns while doing some compile job in the background.

To be exact: I had vlc (1.1 git) play back several flac files and was compiling
qt 4.7 in the background as a test w/ -j5 on an i7 860 . The result was that w/
the decreased granularity it caused noticeable audio buffer underruns while it
worked just fine w/ the default granularity (nothing else touched).

Just wanted to report this early on and hope it helps.

So long,
matthias.

PS. Please cc' as I am not subscribed. Thanks a lot.

Re: [PATCH] sched: Improve latencies under load by decreasing minimum

[Mathieu Desnoyers]

* Matthias Dahl (ml_kernel@mortal-soul.de) wrote:
> Hi.
> 
> I don't know if this is relevant but I just tried this ontop 2.6.35.4 while
> investigating a different problem and it was quite easy to produce audio
> buffer underruns while doing some compile job in the background.
> 
> To be exact: I had vlc (1.1 git) play back several flac files and was compiling
> qt 4.7 in the background as a test w/ -j5 on an i7 860 . The result was that w/
> the decreased granularity it caused noticeable audio buffer underruns while it
> worked just fine w/ the default granularity (nothing else touched).
> 
> Just wanted to report this early on and hope it helps.

Hi Matthias,

Thanks for reporting this. I have a few more questions:

Can you provide:

you full kernel .config

The config values of your sound card:

cat /proc/asound/card0/pcm0p/sub0/hw_params
cat /proc/asound/card0/pcm0c/sub0/hw_params

while you play your audio. (could be other than pcm0p, try to get one which is
not "Closed" while you play) Also providing the dmesg output showing which sound
card driver you are using might help.

Also the output of:
cat /proc/cpuinfo

Also, can you try reproducing the problem with different players ? With
non-git-bleeding-edge vlc versions too ? Can you reproduce this problem while
using "aplay" (a much simpler player) to play wav files ? (I've got an
instrumented version hooked on my tracer that traces underruns in here).

Thanks !

Mathieu

> 
> So long,
> matthias.
> 
> PS. Please cc' as I am not subscribed. Thanks a lot.

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com

Re: [PATCH] sched: Improve latencies under load by decreasing minimum

[Mathieu Desnoyers]

* Mathieu Desnoyers (mathieu.desnoyers@efficios.com) wrote:
> * Matthias Dahl (ml_kernel@mortal-soul.de) wrote:
> > Hi.
> > 
> > I don't know if this is relevant but I just tried this ontop 2.6.35.4 while
> > investigating a different problem and it was quite easy to produce audio
> > buffer underruns while doing some compile job in the background.
> > 
> > To be exact: I had vlc (1.1 git) play back several flac files and was compiling
> > qt 4.7 in the background as a test w/ -j5 on an i7 860 . The result was that w/
> > the decreased granularity it caused noticeable audio buffer underruns while it
> > worked just fine w/ the default granularity (nothing else touched).
> > 
> > Just wanted to report this early on and hope it helps.
> 
> Hi Matthias,
> 
> Thanks for reporting this. I have a few more questions:
> 
> Can you provide:
> 
> you full kernel .config
> 
> The config values of your sound card:
> 
> cat /proc/asound/card0/pcm0p/sub0/hw_params
> cat /proc/asound/card0/pcm0c/sub0/hw_params
> 
> while you play your audio. (could be other than pcm0p, try to get one which is
> not "Closed" while you play) Also providing the dmesg output showing which sound
> card driver you are using might help.
> 
> Also the output of:
> cat /proc/cpuinfo
> 
> Also, can you try reproducing the problem with different players ? With
> non-git-bleeding-edge vlc versions too ? Can you reproduce this problem while
> using "aplay" (a much simpler player) to play wav files ? (I've got an
> instrumented version hooked on my tracer that traces underruns in here).

Also, do you use pulseaudio, alsa directly, or go through OSS ?

Mathieu

> 
> Thanks !
> 
> Mathieu
> 
> > 
> > So long,
> > matthias.
> > 
> > PS. Please cc' as I am not subscribed. Thanks a lot.
> 
> -- 
> Mathieu Desnoyers
> Operating System Efficiency R&D Consultant
> EfficiOS Inc.
> http://www.efficios.com

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com