[ardour-users] [Fwd: Re: Is 64 bit dual core supported and stable yet?]
nando at ccrma.Stanford.EDU
Sun Dec 4 17:36:12 PST 2005
On Sat, 2005-12-03 at 23:33 -0500, Joel White wrote:
> Fernando Lopez-Lezcano wrote:
> >On Sat, 2005-12-03 at 10:49 -0500, Joel White wrote:
> >>I am currently running stock 2.6.14 with the 3800+ X2 (that's me,
> >>below). If I set the smp_affinity of my sound card to one processor,
> >>the "delay of xx usecs exceeds.." messages virtually disappear. Without
> >>that, they pop up regularly, with increasing delay times.
> >Yup, that's the problem of drifting TSC's. Hmmm, most probably you want
> >to pin the jack processes to one processor, not the soundcard.
> Ok, cool. I was wondering about that. I've just tried setting the cpu
> affinity of the jack processes to one processor using taskset, along
> with setting the smp_affinity of the sound card IRQ back to 0x03 (both
> processors). I've been recording 8 tracks at -r 44100 -p 64 -n 2
> (duplex) for over an hour now without an xrun or "delay..." message. I
> think this will give me a good working system for recording.
Sounds very good. Did you reboot? The TSC drift depends on the cpu being
idle and for how long. So right after a reboot you won't see the problem
but it will get worse over time (without reboots and with light
workload). A loaded system will definitely drift very little. I have
note tested vanilla 2.6.14 but on -rt patched kernels the situation
could take a while to show up, once it did it kept getting worse over
time, of course.
> >>As a test, I just got through recording 55+ min of 8 tracks (-r 44100 -p
> >>64 -n 2, duplex) before ardour halted with an xrun and "delay.." error.
> >I sounds to me that -p64 is too low for the stock kernel in any case.
> I don't think so - the xruns and "delay..." values were way outside what
> one would expect given the jack settings (i.e., tens to hundreds of msec).
Could be that vanilla 2.6.14 is better than what I thought.
FYI the latest -rt patch (-rt21) does not choose the TSC for system
timing - that plus a patched jack should also be good without pinning
processes to individual cpus (not to suggest you switch to that).
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