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Date: Thu, 27 Sep 2018 09:19:00 +0800 From: Wanpeng Li <kernellwp@...il.com> To: Dietmar Eggemann <dietmar.eggemann@....com> Cc: Peter Zijlstra <peterz@...radead.org>, Steve Muckle <smuckle@...gle.com>, Miguel de Dios <migueldedios@...gle.com>, Ingo Molnar <mingo@...hat.com>, LKML <linux-kernel@...r.kernel.org>, kernel-team@...roid.com, Todd Kjos <tkjos@...gle.com>, Paul Turner <pjt@...gle.com>, quentin.perret@....com, Patrick Bellasi <Patrick.Bellasi@....com>, Chris.Redpath@....com, Morten Rasmussen <Morten.Rasmussen@....com>, John Dias <joaodias@...gle.com>, Wanpeng Li <wanpengli@...cent.com> Subject: Re: [PATCH] sched/fair: vruntime should normalize when switching from fair On Thu, 27 Sep 2018 at 06:38, Dietmar Eggemann <dietmar.eggemann@....com> wrote: > > Hi, > > On 09/26/2018 11:50 AM, Wanpeng Li wrote: > > Hi Dietmar, > > On Tue, 28 Aug 2018 at 22:55, Dietmar Eggemann <dietmar.eggemann@....com> wrote: > >> > >> On 08/27/2018 12:14 PM, Peter Zijlstra wrote: > >>> On Fri, Aug 24, 2018 at 02:24:48PM -0700, Steve Muckle wrote: > >>>> On 08/24/2018 02:47 AM, Peter Zijlstra wrote: > >>>>>>> On 08/17/2018 11:27 AM, Steve Muckle wrote: > > [...] > > >>>>>>>> - later, when the prio is deboosted and the task is moved back > >>>>>>>> to the fair class, the fair rq's min_vruntime is added to > >>>>>>>> the task's vruntime, even though it wasn't subtracted earlier. > > > > Could you point out when the fair rq's min_vruntime is added to the > > task's vruntime in your *later* scenario? attach_task_cfs_rq will not > > do that the same reason as detach_task_cfs_rq. fair task's > > sched_remote_wakeup is false which results in vruntime will not be > > renormalized in enqueue_entity. > > The cfs_rq->min_vruntime is still added to the se->vruntime in > enqueue_task_fair(). I understand what your patch done, On your CPU4: scheduler_ipi() -> sched_ttwu_pending() -> ttwu_do_activate() => p->sched_remote_wakeup should be false, so ENQUEUE_WAKEUP is set, ENQUEUE_MIGRATED is not -> ttwu_activate() -> activate_task() -> enqueue_task() -> enqueue_task_fair() -> enqueue_entity() bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATE) so renorm is false in enqueue_entity(), why you mentioned that the cfs_rq->min_vruntime is still added to the se->vruntime in enqueue_task_fair()? Regards, Wanpeng Li
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