Re: CONFIG_PREEMPT and server workloads

[Takashi Iwai <tiwai@suse.de>]

At Fri, 19 Mar 2004 17:12:55 -0500,
Robert Love wrote:
> 
> 
> > Is one of these yours?  My machine has 3 (but only one soundcard) ;)
> > 
> > %  find /proc/asound/ -name xrun_debug -ls
> >   4480    0 -r--r--r--   1 root     root            0 Mar 19 16:00 /proc/asound/card0/pcm1c/xrun_debug
> >   4470    0 -r--r--r--   1 root     root            0 Mar 19 16:00 /proc/asound/card0/pcm0c/xrun_debug
> >   4462    0 -r--r--r--   1 root     root            0 Mar 19 16:00 /proc/asound/card0/pcm0p/xrun_debug
> > 
> > (Are these 3 different controls, or 3 places to set the same variable?)
> 
> Heh :)
> 
> I suspect I need debugging enabled.

yes, please turn on CONFIG_SND_DEBUG.

these files appear in each PCM stream, so that only one of them can be
activated.  for example, pcm0p is the first PCM for playback, pcm1c
the second PCM for capture.

in the latest version of ALSA (the patchset will be submitted by
Jaroslav hopefully soon later), the debug messages are suppressed
until xrun_debug > 0 is set, because in many cases they are triggered
by the sloppy irq handler and harmless.
when xrun_debug > 1, the driver will show stacktraces together with
the xrun (overrun/underrun) notifications.

there is a new document, Documentation/sound/alsa/Procfile.txt, for
describing these and other proc files of ALSA.


Takashi