[linux-audio-user] Which kernel for low latency and kernel 2.6.1-mm# problems

Takashi Iwai tiwai at suse.de
Wed Jan 21 06:37:47 EST 2004

At Wed, 21 Jan 2004 03:01:19 -0800,
Andrew Morton wrote:
> > I just wanted to elaborate abit; -R in the argument line indicates that jack 
> > should be running SCHED_FIFO, and since there are no specific settings for 
> > period-size and number of periods, jack is probably defaulting to 2-periods 
> > and 1024 samples period size. 2.4 works rather reliably with period-sizes 
> > quite a bit smaller than that. I think 256 is commonly used, with good 
> > hardware+drivers I suppose you could go even lower.
> I don't know what these numbers mean...
> What does this transalate to in interval-in-milliseconds, and after how
> many milliseconds delay will an underrun occur?
> And what else is happening on the system at the time?

a few months ago before 2.6.0 was released, i tested the audio latency
with different kernels.  the result was shown in the internal
conference in SUSE, and i totally forgot to release the data until now
maybe it will show you other aspects.

here you can find the slides


some notes:

  - the red line of the graph is the buffer size - when the plot
    overcomes this line, the buffer underrun occurs, aka sound
  - performed on Athlon 2200+ / 256MB / SB live
  - the kernel tested at that time was slightly old, 2.6.0-test10,
    so the result with the latest kernel may differ.
  - suse 2.4 kernel runs with HZ=1000 and O(1) scheduler

Takashi Iwai <tiwai at suse.de>		ALSA Developer - www.alsa-project.org

More information about the Linux-audio-user mailing list