Messages in this thread | | | Date | Wed, 6 Dec 2017 12:40:28 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v4] sched: Update runnable propagation rule |
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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.du@intel.com> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: Mike Galbraith <efault@gmx.de> > Cc: Chris Mason <clm@fb.com> > Cc: Linus Torvalds <torvalds@linux-foundation.org> > Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> > Cc: Josef Bacik <josef@toxicpanda.com> > Cc: Ben Segall <bsegall@google.com> > Cc: Paul Turner <pjt@google.com> > Cc: Tejun Heo <tj@kernel.org> > Cc: Morten Rasmussen <morten.rasmussen@arm.com> > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > Link: http://lkml.kernel.org/r/20171019150442.GA25025@linaro.org
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Ingo, can you stuff this in sched/urgent ?
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