[PD] using chrt on pd to get rid of DIO errors

Rich E reakinator at gmail.com
Sat Nov 24 14:30:56 CET 2007

This is not a very good solution, since I think it causes the JACK to lock
up occasionally, but so far I have no clue why pd is having this problem.
It appears to only happen with JACK (ALSA runs fine), and I do not have
similar xruns with other programs running at the same time (ex. Ardour.
Also, qjackctl shows no xruns).  I get xruns about once a second, then I do
the command "chrt -p 60 [whatever pd's pid is]" and all xruns go away.

Anyone know where to look for a solution?  It is no good having the audio
dropped or, worse, pd crashing occasionally.


On Nov 19, 2007 8:34 PM, Rich E <reakinator at gmail.com> wrote:

> After setting up ubuntustudio (7.04) with a real-time kernel (
> 2.6.20-16-realtime), I was experiencing DIO errors every few seconds.
> Exploring this taught me alot about how to set priorities on a real-time
> kernel, mainly with the command 'chrt'.  However, I don't think it is meant
> to be used directly on an application, since there might be parts of the
> application that are not supposed to run in real-time at a high priority.
> Nonetheless, running:
> r at pal:/etc/sysconfig$ pidof pd
> 12079
> r at pal:/etc/sysconfig$ chrt -p 60 12079
> sets pd running as:
> r at pal:/etc/sysconfig$ chrt -p 12079
> pid 12079's current scheduling policy: SCHED_RR
> pid 12079's current scheduling priority: 60
> and the xruns go away.  I don't know too much about the different threads
> pd is running on, but I was under the impression that pd is supposed to
> start in real-time with a high priority.  Yet, due to the apperant changes
> from chrt, I would think that it was not running in real-time.  I've tried
> this on versions 0.40-3 and 0.41-7, and real-time scheduling is not
> specifically turned off in the pd start-up settings.
> Any thoughts?
> regards,
> rich
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