[linux-audio-dev] Linux kernel HZ, audio latency and how to measure?
rlrevell at joe-job.com
Sat Aug 19 00:28:12 UTC 2006
On Fri, 2006-08-18 at 20:26 -0400, Stephen Sinclair wrote:
> I've certainly seen setitimer()-driven sleeping get much better
> response time on a kernel compiled to 1000 Hz (with preemption) over
> one compiled to 100 Hz (without preemption).
> >From this, I think it should be possible to say that one could read
> the audio card with smaller buffers more quickly, reducing latency.
> But I haven't made tests using audio, specifically, so I won't say
> more. I suspect the kernel driver and userspace API (ALSA or
> whatever) might need to be made to take advantage of it, but I know
> little about ALSA internals.
Audio doesn't use setitimer()-driven sleeping. It's interrupt-driven,
> On 8/18/06, Paul Davis <paul at linuxaudiosystems.com> wrote:
> > On Fri, 2006-08-18 at 23:10 +0700, Mulyadi Santosa wrote:
> > > Is there any relationship between kernel HZ and audio timing? I imagine
> > no. or almost none.
> > recording audio doesn't involve using the system timer at all. the only
> > clock involved is the sample clock that drives the audio interface.
> > having HZ set too high could conceivably make the system more likely to
> > xrun, but this is not likely with a fully RT kernel.
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