Audio skipping with 2.6.24.4 and 2.6.25-rc9

Audio skipping with 2.6.24.4 and 2.6.25-rc9

[Frederik Himpe]

I'm experiencing a lot of problems with audio skipping on my system. I am 
using Rhythmbox as an audio player and have Compiz active. Whenever I 
maximise or restore a maximised real transparent gnome-terminal, audio 
skips. Compared to other normal applications, restoring the transparent 
console is also slow (it takes a few seconds before the window appears).

I ran cfs-debug-info-clear.sh, and the reproduced the problem 3 times by 
restoring and minimising a gnome-terminal window. After that I ran cfs-
debug-info.sh, and I uploaded the information here: 
http://artipc10.vub.ac.be/cfs-debug-info-2008.04.12-18.00.20.gz

This problem happens with both 2.6.24.4 as with 2.6.25-rc9 (the debugging 
information is from the latter version).

-- 
Frederik Himpe

Re: Audio skipping with 2.6.24.4 and 2.6.25-rc9

[Markus Trippelsdorf]

On Sat, Apr 12, 2008 at 04:13:01PM +0000, Frederik Himpe wrote:
> I'm experiencing a lot of problems with audio skipping on my system. I am 
> using Rhythmbox as an audio player and have Compiz active. Whenever I 
> maximise or restore a maximised real transparent gnome-terminal, audio 
> skips. Compared to other normal applications, restoring the transparent 
> console is also slow (it takes a few seconds before the window appears).
> ...
> This problem happens with both 2.6.24.4 as with 2.6.25-rc9 (the debugging 
> information is from the latter version).
> 

Try to disable the group scheduler in your kernel configuration. 
It solved the audio skipping problem on my machine...
-- 
Markus

Re: Audio skipping with 2.6.24.4 and 2.6.25-rc9

[Frederik Himpe]

On Sat, 12 Apr 2008 19:51:24 +0200, Markus Trippelsdorf wrote:

> On Sat, Apr 12, 2008 at 04:13:01PM +0000, Frederik Himpe wrote:
>> I'm experiencing a lot of problems with audio skipping on my system. I
>> am using Rhythmbox as an audio player and have Compiz active. Whenever
>> I maximise or restore a maximised real transparent gnome-terminal,
>> audio skips. Compared to other normal applications, restoring the
>> transparent console is also slow (it takes a few seconds before the
>> window appears). ...
>> This problem happens with both 2.6.24.4 as with 2.6.25-rc9 (the
>> debugging information is from the latter version).
>> 
>> 
> Try to disable the group scheduler in your kernel configuration. It
> solved the audio skipping problem on my machine...

I think I have it disabled already?

$ zcat /proc/config.gz | grep GROUP
# CONFIG_CGROUPS is not set
# CONFIG_GROUP_SCHED is not set

Or am I missing something?

-- 
Frederik Himpe

Re: Audio skipping with 2.6.24.4 and 2.6.25-rc9

[Markus Trippelsdorf]

On Sat, Apr 12, 2008 at 06:06:24PM +0000, Frederik Himpe wrote:
> On Sat, 12 Apr 2008 19:51:24 +0200, Markus Trippelsdorf wrote:
> 
> > On Sat, Apr 12, 2008 at 04:13:01PM +0000, Frederik Himpe wrote:
> >> I'm experiencing a lot of problems with audio skipping on my system. I
> >> am using Rhythmbox as an audio player and have Compiz active. Whenever
> >> I maximise or restore a maximised real transparent gnome-terminal,
> >> audio skips. Compared to other normal applications, restoring the
> >> transparent console is also slow (it takes a few seconds before the
> >> window appears). ...
> >> This problem happens with both 2.6.24.4 as with 2.6.25-rc9 (the
> >> debugging information is from the latter version).
> >> 
> >> 
> > Try to disable the group scheduler in your kernel configuration. It
> > solved the audio skipping problem on my machine...
> 
> I think I have it disabled already?
> 
> $ zcat /proc/config.gz | grep GROUP
> # CONFIG_CGROUPS is not set
> # CONFIG_GROUP_SCHED is not set
> 
> Or am I missing something?

Yeah, I figured that out after I had send you my brilliant suggestion.
Sorry.

-- 
Markus

Re: Audio skipping with 2.6.24.4 and 2.6.25-rc9

[Carlos R. Mafra]

On Sat 12.Apr'08 at 16:13:01 +0000, Frederik Himpe wrote:
> I'm experiencing a lot of problems with audio skipping on my system. I am 
> using Rhythmbox as an audio player and have Compiz active. Whenever I 
> maximise or restore a maximised real transparent gnome-terminal, audio 
> skips. Compared to other normal applications, restoring the transparent 
> console is also slow (it takes a few seconds before the window appears).
> 
> I ran cfs-debug-info-clear.sh, and the reproduced the problem 3 times by 
> restoring and minimising a gnome-terminal window. After that I ran cfs-
> debug-info.sh, and I uploaded the information here: 
> http://artipc10.vub.ac.be/cfs-debug-info-2008.04.12-18.00.20.gz
> 
> This problem happens with both 2.6.24.4 as with 2.6.25-rc9 (the debugging 
> information is from the latter version).

I once learned ( http://lkml.org/lkml/2008/2/29/179 )
that the CFS would have something to do with the latencies I was
observing in my system if se.wait_max was bigger than 40 msecs.
It would be an "anomaly" in CFS.

But in the log you uploaded you have only two se.wait_max greater than
40 msecs

[mafra@localhost:~]$ grep se.wait_max cfs-debug-info-2008.04.12-18.00.20 |awk '{ {if ($3 > 40.000000) print $3} }'
44.153039
50.841370

As these numbers are only a bit greater than 40, I guess your problem is not
related to the CFS scheduler.

Can you try latencytop? ( www.latencytop.org )

Bye,
Carlos

Re: Audio skipping with 2.6.24.4 and 2.6.25-rc9

[Frederik Himpe]

On Sat, 12 Apr 2008 16:19:14 -0300, Carlos R. Mafra wrote:

> But in the log you uploaded you have only two se.wait_max greater than
> 40 msecs
> 
> [mafra@localhost:~]$ grep se.wait_max cfs-debug-info-2008.04.12-18.00.20
> |awk '{ {if ($3 > 40.000000) print $3} }' 44.153039
> 50.841370
> 
> As these numbers are only a bit greater than 40, I guess your problem is
> not related to the CFS scheduler.
> 
> Can you try latencytop? ( www.latencytop.org )

I'm not too sure how I should use latencytop and interpret its results. I 
start latencytop, and reproduce the problem while rhythmbox is playing. It 
seems that it automatically changes the selected application in the bottom 
list after a few seconds, probably based on the CPU usage, where it 
selects most of the time either compiz or X. The upper half of latencytop 
is always empty, for all applications. In the lower half, it shows for all 
applications something like:

Process X (7972)
Scheduler: waiting for cpu     43.5 msec         43.5 msec

Only the times differ between the different processes.

And that's all...

-- 
Frederik Himpe

Re: Audio skipping with 2.6.24.4 and 2.6.25-rc9

[Carlos R. Mafra]

On Sat 12.Apr'08 at 20:19:55 +0000, Frederik Himpe wrote:
> On Sat, 12 Apr 2008 16:19:14 -0300, Carlos R. Mafra wrote:
> 
> > But in the log you uploaded you have only two se.wait_max greater than
> > 40 msecs
> > 
> > [mafra@localhost:~]$ grep se.wait_max cfs-debug-info-2008.04.12-18.00.20
> > |awk '{ {if ($3 > 40.000000) print $3} }' 44.153039
> > 50.841370
> > 
> > As these numbers are only a bit greater than 40, I guess your problem is
> > not related to the CFS scheduler.
> > 
> > Can you try latencytop? ( www.latencytop.org )
> 
> I'm not too sure how I should use latencytop and interpret its results. I 
> start latencytop, and reproduce the problem while rhythmbox is playing. It 
> seems that it automatically changes the selected application in the bottom 
> list after a few seconds, probably based on the CPU usage, where it 
> selects most of the time either compiz or X. The upper half of latencytop 
> is always empty, for all applications. In the lower half, it shows for all 
> applications something like:
> 
> Process X (7972)
> Scheduler: waiting for cpu     43.5 msec         43.5 msec
> 
> Only the times differ between the different processes.

Did you try with the git version of latencytop?
I remember that once I downloaded latencytop from the website 
and the upper half of latencytop was also always empty, and
that the git version was better and showed the latencies.

Re: Audio skipping with 2.6.24.4 and 2.6.25-rc9

[Frans Pop]

Frederik Himpe wrote:
> I'm not too sure how I should use latencytop and interpret its results. I
> start latencytop, and reproduce the problem while rhythmbox is playing. It
> seems that it automatically changes the selected application in the bottom
> list after a few seconds, probably based on the CPU usage, where it
> selects most of the time either compiz or X. The upper half of latencytop
> is always empty, for all applications. In the lower half, it shows for all
> applications something like:
> 
> Process X (7972)
> Scheduler: waiting for cpu     43.5 msec         43.5 msec
> 
> Only the times differ between the different processes.

Had the same problem until just a few days ago when I figured it out mostly 
by accident.

You need to 'echo -n 1 > /proc/sys/kernel/latencytop' to enable latencytop 
tracing to get more useful info. It's something that's badly documented 
unfortunately. Make sure you disable it again when you're done so you don't 
keep the tracing overhead.
Not sure why starting the latencytop application does not enable tracing 
automatically, or at least provides an option to do so.

I also agree that the automatic switches to other apps are strange. Adding a 
particular app name or PID on the command line does not seem to have any 
effect.

Unfortunately the latencytop website also misses usage info and seems 
generally outdated as it still says that a patch to the kernel is required.

CC'ing Arjen in the hope that he can find some time to improve this.

Cheers,
FJP