[linux-audio-dev] Re: [vst-plugins] Plugin server

Fernando Pablo Lopez-Lezcano nando at ccrma.Stanford.EDU
Wed Dec 11 17:13:01 UTC 2002


On Sun, 2002-12-08 at 16:14, Kai Vehmanen wrote:
> On Sun, 8 Dec 2002, Paul Davis wrote:
> 
> > you also haven't addressed kernel scheduling issues; the context
> > switch doesn't happen till the kernel has decided what task is going
> > to run next. if it picks the wrong one, for whatever reason, then
> > you/we lose. right now, it picks the wrong one too often, even with
> > SCHED_FIFO+mlockall.
> 
> Btw; have you tried the O(1) scheduler? It has a number of interesting
> charasteristics from an audio app developer's pov [1]:

I tried it (using the Con Kolivas patches on top of 2.4.20). I still get
xruns in jackd, although that particular patchset (plus the drm lowlat
patches) seems to keep them to more reasonable values at least in a
short test I just did. I managed to also hang the machine, after running
jackd + qjackconnect + freqtweak + ams for a while I got greedy and
started ardour - created a new session and when I went to connect things
in qjackconnect the machine stopped... it still responds to alt-sysrq-b.
BTW, with latest versions of alsa the hanging problems seems to happen
less frequently so it may be some interaction between alsa and the
kernel (hangs do not seem to happen in 2.4.19).

Besides that, it looks like the O(1) scheduler is less responsive to
user interaction in certain cases. While doing an alsa driver compile
the mouse was freezing for fractions of a second at a time (this was
during the depend phase, actually compiling the modules did not have
that effect). 

[anyone out there has a patch to schedutils to make them work with the
O(1) scheduler?, mine just report all tasks as Other]

-- Fernando





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