lkml.org 
[lkml]   [2018]   [Sep]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH] sched/fair: vruntime should normalize when switching from fair
On Thu, 27 Sep 2018 at 06:38, Dietmar Eggemann <dietmar.eggemann@arm.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@arm.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

\
 
 \ /
  Last update: 2018-09-27 03:19    [W:1.807 / U:0.040 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site