Re: About group scheduling for SCHED_DEADLINE

From: Peter Zijlstra
Date: Mon Oct 10 2016 - 07:08:33 EST

On Mon, Oct 10, 2016 at 12:15:58PM +0200, Peter Zijlstra wrote:
> However, I think there's a third alternative. I have memories of a paper
> from UNC (I'd have to dig through the site to see if I can still find
> it) where they argue that for a hierarchical (G-)FIFO you should use
> minimal concurrency, that is run the minimal number of (v)cpu servers.
> This would mean we give a single CBS parameter and carve out the minimal
> number (of max CBS) (v)cpu that fit in that.
> I'm just not sure how the random affinity crap works out for that, if we
> have the (v)cpu servers migratable in the G-EDF and migrate to whatever
> is demanded by the task at runtime it might work, but who knows..
> Analysis would be needed I think.

Hurm,.. thinking slightly more on this, this ends up being a DL task
with random affinity, which is problematic IIRC.