Re: [linux-audio-dev] user lowlatency kernel experience

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Subject: Re: [linux-audio-dev] user lowlatency kernel experience
From: Roger Larsson (roger.larsson_AT_norran.net)
Date: Thu Jun 14 2001 - 23:01:28 EEST


Hi,

You could try to run with SCHED_RR since it is fairer...
One alternative approach could prioritize according to
expected runtime, longer time - lower prio. To see if it
helps in this case.
Third alternative could be to use higher priorities the closer
you get to the output.

in
--| A - prio x |--| B - prio x+1 |--| C - prio x+2 |--
                                                                          out

In this way the scheduler won't start A nor B if there is
something in the input for C... (could work...)

/RogerL

On Thursday 14 June 2001 18:54, you wrote:
> An example:
>
> I've got a (unix) pipeline of filters followed by a sound player,
> mostly written by myself, with no consideration of scheduling
> fairness. When I run it with real-time priority, it consistently has
> underruns about every 1/4 sec. The problem is that the filters are
> working with fairly large (8k sample) chunks, and naturally the player
> underruns while the filters are working.
>
> One of these days, I'll fix the filters to have some concept of
> fairness. Meantime, I just run at nice level -20, and get no dropouts
> at all, even with 10 copies of emacs open and a kernel compilation
> running. This using a kernel with low latency patches applied, of
> course.
>
> Hopefully someone will bite the bullet and write a linux scheduler
> that supports a hybrid of realtime and fairness and that has adjustable
> parameters.
>
> /s jsr
>
> On Thu, 14 Jun 2001, Joakim Verona wrote:
> > ... In my opinion, different applications
> > can never be assumed to be well-behaved and cooperative. Then we will
> > wind up with systems behaving like windows 3.11 and the old Macintoshes.

-- 
Roger Larsson
Skellefteċ
Sweden


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