Re: periods and deadlines in SCHED_DEADLINE

[Peter Zijlstra <peterz@infradead.org>]

On Sun, 2010-07-11 at 08:42 +0200, Bjoern Brandenburg wrote:
> 
> If you want to do G-EDF with limited and different budgets on each CPU
> (e.g., G-EDF tasks may only run for 100 out of 1000 ms on CPU 0, but
> for 400 out of 1000 ms on CPU 1), then you are entering the domain of
> restricted-supply scheduling, which is significantly more complicated
> to analyze (see [1,2]). 

Without having looked at the refs, won't the soft case still have
bounded tardiness? Since the boundedness property mostly depends on
u<=1, that is, as long as we can always run everything within the
available time we won't start drifting.

> As far as I know there is no exiting analysis for "almost G-EDF",
> i.e.,  the case where each task may only migrate among a subset of the
> processors (= affinity masks), except for the special case of
> clustered EDF (C-EDF), wherein the subsets of processors are
> non-overlapping. 

Right, affinity masks are a pain, hence I proposed to limit that to
either 1 cpu (yielding fully paritioned) or the full cluster.

That will leave us with only having to stack a partitioned and global
scheduler on top of each other, and per the previous point, I think that
ought to work out trivially for soft, hard otoh will get 'interesting'.