* Peter Zijlstra <pet...@infradead.org> wrote:
> On Thu, Nov 16, 2017 at 03:21:52PM +0100, Vincent Guittot wrote:
> > Unlike running, the runnable part can't be directly propagated through
> > the hierarchy when we migrate a task. The main reason is that runnable
> > time can be shared with other sched_entities that stay on the rq and
> > this runnable time will also remain on prev cfs_rq and must not be
> > removed.
> >
> > Instead, we can estimate what should be the new runnable of the prev
> > cfs_rq and check that this estimation stay in a possible range. The
> > prop_runnable_sum is a good estimation when adding runnable_sum but
> > fails most often when we remove it. Instead, we could use the formula
> > below instead:
> >
> > gcfs_rq's runnable_sum = gcfs_rq->avg.load_sum / gcfs_rq->load.weight
> >
> > which assumes that tasks are equally runnable which is not true but
> > easy to compute.
> >
> > Beside these estimates, we have several simple rules that help us to filter
> > out wrong ones:
> >
> > - ge->avg.runnable_sum <= than LOAD_AVG_MAX
> > - ge->avg.runnable_sum >= ge->avg.running_sum (ge->avg.util_sum <<
> > LOAD_AVG_MAX)
> > - ge->avg.runnable_sum can't increase when we detach a task
> >
> > Cc: Yuyang Du <yuyang...@intel.com>
> > Cc: Ingo Molnar <mi...@kernel.org>
> > Cc: Mike Galbraith <efa...@gmx.de>
> > Cc: Chris Mason <c...@fb.com>
> > Cc: Linus Torvalds <torva...@linux-foundation.org>
> > Cc: Dietmar Eggemann <dietmar.eggem...@arm.com>
> > Cc: Josef Bacik <jo...@toxicpanda.com>
> > Cc: Ben Segall <bseg...@google.com>
> > Cc: Paul Turner <p...@google.com>
> > Cc: Tejun Heo <t...@kernel.org>
> > Cc: Morten Rasmussen <morten.rasmus...@arm.com>
> > Signed-off-by: Vincent Guittot <vincent.guit...@linaro.org>
> > Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
> > Link: http://lkml.kernel.org/r/20171019150442.ga25...@linaro.org
>
> Acked-by: Peter Zijlstra (Intel) <pet...@infradead.org>
>
> Ingo, can you stuff this in sched/urgent ?
Yeah, I've queued up in tip:sched/urgent.
Thanks,
Ingo
