Re: [PATCH] sched: fix how RT task is pulled

[Mike Galbraith <efault@gmx.de>]

On Tue, 2011-05-17 at 22:47 +0800, Hillf Danton wrote:
> On Tue, May 17, 2011 at 10:35 AM, Yong Zhang <yong.zhang0@gmail.com> wrote:
> > On Sun, May 15, 2011 at 10:50 AM, Hillf Danton <dhillf@gmail.com> wrote:
> >> When pulling RT task for a given runqueue, if it is already overloaded
> >> with RT tasks, the pull operation could be avoided at the moment.
> >>
> >> btw, it looks like a typo?
> >
> > No.
> >
> > Below is how rt_overloaded() is realized:
> > static inline int rt_overloaded(struct rq *rq)
> > {
> >        return atomic_read(&rq->rd->rto_count);
> > }
> >
> > You can notice it's about the overload of the very root_domain.
> >
> Well, why is it going no head if not overloaded?

To avoid examining masks (maybe huge) routinely.  Challenge is to
improve oddball case (overload) without injuring the common case.

	-Mike