Re: [linux-audio-dev] another kernel patch?

New Message Reply About this list Date view Thread view Subject view Author view Other groups

Subject: Re: [linux-audio-dev] another kernel patch?
From: Jack O'Quin (joq_AT_io.com)
Date: Sat Nov 29 2003 - 19:50:31 EET


Paul Davis <paul_AT_linuxaudiosystems.com> writes:

> the problem is not (just?) the time that the scheduler takes. its that
> its decision making process is opaque. when jackd runs, it knows for
> certain which pid/tid to run next. we don't want to cede control of
> that back to the kernel scheduler.

No scheduler that I've ever seen, written, or heard of is going to
accept JACK's opinion on this subject as anything more than a strong
hint. The scheduler is the main loop of the entire system, *it*
decides what to run next.

Suggestions are welcome, but JACK truly does *not* know for certain
what to run next. An interrupt could intervene and make a
higher-priority realtime process ready. Or, some other processor
could unlock such a thread. At the very least, there probably needs
to be code in the return path from the system call like the old Unix
logic of testing `runrun' and calling sched().

> i think i've mentioned before that i'd like to do a paper on JACK
> someday for Usenix, with a focus on its capabilities for "user space
> cooperative real-time scheduling", or something like that.

Sounds good.

-- 
  joq


New Message Reply About this list Date view Thread view Subject view Author view Other groups

This archive was generated by hypermail 2b28 : Sat Nov 29 2003 - 19:48:22 EET