Subject: Re: [linux-audio-user] Which kernel for low latency and kernel 2.6.1-mm# problems
From: Andrew Morton (akpm_AT_osdl.org)
Date: Wed Jan 21 2004 - 13:01:19 EET
Robert Jonsson <robert.jonsson_AT_dataductus.se> wrote:
>
> On Wednesday 21 January 2004 11.38, Steve Harris wrote:
> > On Wed, Jan 21, 2004 at 02:20:04AM -0800, Andrew Morton wrote:
> > > > need to find these too.) Last I heard Andrew (cc:ed) thought it worked
> > > > as good as 2.4, except for some rare corner cases.
> > >
> > > Not as rare as one would like. But not too bad unless you're doing heavy
> > > filesytem work at the same time.
> > >
> > > > On Wednesday 21 January 2004 03.38, Glenn McCord wrote:
> > > > > James Stone wrote:
> > > > > >>I run jack with:
> > > > > >>jackstart -R -v -d alsa -d hw:0
> > > > > >>
> > > > > >>...and I get xruns whenever I open a program, move windows around.
> > > > > >> Hell sometimes it does it when I'm just looking at it. More
> > > > > >> specifically, if I want to record in ardour, jack chokes up an
> > > > > >> xrun after about 2 seconds.
> > >
> > > Is `jack' running with realtime priority, or is it merely SCHED_OTHER?
> >
> > Its running SCHED_FIFO in this case.
> >
> > - Steve
>
> I'm not sure you're reading this list Andrew so I'll send directly also.
Thanks. I'm not scared of email ;)
> 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?
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