[Fwd: Re: [PD] Low Latency patch for kernel anyone?]

Aymeric stm-sq at bleu255.com
Mon Sep 6 13:54:25 CEST 2004

and a little note from ck's site about preemption in 2.6 for those who
still wonder if they should use it or not.

I recommend disabling preemption in the kernel configuration unless you
have a specific low latency requirement! It causes poorly written
applications to misbehave far more. The gains in lateny with in-kernel
preemption in 2.6 would not be noticable to a human, unlike 2.4 which
had much larger latencies in the kernel. For serious audio work, video
capture etc, you should enable preempt."


and interesting articles about preempt or not (so now you can get even
more confused)




ps: maybe it would be nice "one day" to try to gather pd "benchmarks" to
see what the best could be taken from 2.6 kernels and how, everytime a
latency talk is started it's always dying into mass-confusion. I think
it would be really great to have online somewhere, a kernel
recommandation guide for pd that has not be written for 2.4 and planet
ccrma (no offense, just looking for fresh docs).

ps: i'm aware such talks are mostly happening in linux-audio lists, but
my point here is to make this whole information friendly available for
users, as a single note about recommanded software setup. This could be
even extended to Gem and pdp/pidip, pointing on which drivers are the
most efficient etc etc ... just a simple "pd setup guideline".

On Mon, Sep 06, 2004 at 01:19:50PM +1000, Luke Yelavich wrote :
> On Mon, Sep 06, 2004 at 03:36:53PM EST, Ian Smith-Heisters wrote:
> > Isn't low latency part of the kernel as of 2.6? If it's not 
> > automatically turned on, it's an option in the config. I guess I'm 
> > assuming you're talking about THE low latency patch that we used to use 
> > on 2.4, but perhaps you're looking for any new low latency patches...?
> You are thinking of the preemptable kernel config option. Unfortunately, wit
> this option turned on, it is still not possible to get as low a latency as it
> is on 2.4. There is however, a patch that is being worked on to address this
> issue, and while it is quite stable now, it still has some way to go, as more
> problems are being found all the time.
> Check out the following URL for more info.
> http://www.affenbande.org/~tapas/linux-2.6.x-ll.html
> -- 
> Luke Yelavich
> http://www.audioslack.com
> luke at audioslack.com
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