sched_ule performance on single CPU

[Oliver Fromme]

Unga <unga888 at yahoo.com> wrote:
 > When open an pdf has two types of scenarios in
 > FreeBSD:
 > 1. When X run as a realtime-prio process, X go mad and
 > swallow up almost all of CPU cycles, making audio
 > hiccups. 

That's expected.  Running the X server with rtprio is not
a good idea.  There's no reason to do that.

 > 2. When X run as a normal-prio process, X behaves well
 > and rarely gets an audible hiccup.

That's good.  :-)

 > Why X behave different under different priority
 > categories? Isn't this scheduler related?

Very simple:  Sometimes the X server consumes lots of CPU
for a short time.  If it runs with rtprio, then no other
process gets a chance to execute, so your audio program
will starve.

My recommendation is to not use rtprio or renice.  I think
many people who try to use them are making things worse.
(In fact I think rtprio and idprio should die.)

 > I wonder the issue I mentioned, open a pdf while
 > playback audio, is it a issue on Apple Mac OSX? Could
 > somebody give some light here who uses an Apple Mac
 > OSX on this list?

OSX has a vastly different kernel, scheduler, I/O system,
audio drivers and so on.  It's a completely different
animal.

Have you tried increasing the audio driver's buffersize?
It probably helps to alleviate your problem.  I think
OSX sizes the buffer dynamically (not sure though).

Best regards
   Oliver

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