Re: [RFC][PATCH] SCHED_ISO for interactivity

Con Kolivas (
Mon, 14 Jul 2003 10:13:12 +1000

On Mon, 14 Jul 2003 06:03, Daniel Phillips wrote:
> On Saturday 12 July 2003 17:49, William Lee Irwin III wrote:
> > On Fri, Jul 11, 2003 at 08:53:38PM +1000, Con Kolivas wrote:
> > > Wli coined the term "isochronous" (greek for same time) for a real time
> > > task that was limited in it's timeslice but still guaranteed to run.
> > > I've decided to abuse this term and use it to name this new policy in
> > > this patch. This is neither real time, nor guaranteed.
> >
> > I didn't coin it; I know of it from elsewhere.
> Right, for example, USB has an isochronous transfer facility intended to
> support media applications, e.g., cameras, that require realtime
> bandwidth/latency guarantees. The thing is, such guarantees have to be
> end-to-end in the media pipeline. Sound is just one of the applications
> that needs the kind of realtime support we (or more properly, Davide) just
> proposed.

I'm not looking at creating a true realtime policy of any sort. Mine is more a
dynamic policy change to an interactive state that is sustained, which gives
no more capabilities to a normal user process than they can currently get on
SCHED_NORMAL tasks. Audio will definitely get priority... along with any
other interactive task, but not in a real time fashion. Basically they
effectively get a nice -5 unless they do the wrong thing.


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