Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks
Date	2016-06-17 18:10 +0200
Message-ID	<rL4vf-jd-3@gated-at.bofh.it> (permalink)
References	<rL0KZ-6mx-9@gated-at.bofh.it> <rL0L0-6mx-23@gated-at.bofh.it> <rL2D8-7yf-9@gated-at.bofh.it> <rL2Wt-7ET-29@gated-at.bofh.it>
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On Fri, Jun 17, 2016 at 04:28:14PM +0200, Peter Zijlstra wrote:
> On Fri, Jun 17, 2016 at 04:09:01PM +0200, Vincent Guittot wrote:
> > >
> > > Scenario 1: switch to fair class
> > >
> > >   p->sched_class = fair_class;
> > >   if (queued)
> > >     enqueue_task(p);
> > >       ...
> > >         enqueue_entity()
> > >           enqueue_entity_load_avg()
> > >             migrated = !sa->last_update_time (true)
> > >             if (migrated)
> > >               attach_entity_load_avg()
> > >   check_class_changed()
> > >     switched_from() (!fair)
> > >     switched_to()   (fair)
> > >       switched_to_fair()
> > >         attach_entity_load_avg()
> 
> > > @@ -733,18 +737,21 @@ void post_init_entity_util_avg(struct sc
> > >                 }
> > >                 sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
> > >         }
> > > +
> > > +       update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, false);
> > > +       attach_entity_load_avg(cfs_rq, se);
> > 
> > A new RT task will be attached and will contribute to the load until
> > it decays to 0

> > Should we detach it for non cfs task ?

Right, an attach + detach, which basically ends up being:

> > We just want to update
> > last_update_time of RT task to something different from 0

this. That's the same as starting as fair and then doing
switched_from_fair().

So yes, ho-humm, how to go about doing that bestest. Lemme have a play.

Thread

[PATCH 0/4] sched/fair: Fix PELT wobblies Peter Zijlstra <peterz@infradead.org> - 2016-06-17 14:10 +0200
  [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Peter Zijlstra <peterz@infradead.org> - 2016-06-17 14:10 +0200
    Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Vincent Guittot <vincent.guittot@linaro.org> - 2016-06-17 16:10 +0200
      Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Peter Zijlstra <peterz@infradead.org> - 2016-06-17 16:30 +0200
        Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Peter Zijlstra <peterz@infradead.org> - 2016-06-17 18:10 +0200
          Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Vincent Guittot <vincent.guittot@linaro.org> - 2016-06-17 18:20 +0200
          Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Peter Zijlstra <peterz@infradead.org> - 2016-06-17 18:20 +0200
            Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Yuyang Du <yuyang.du@intel.com> - 2016-06-20 09:00 +0200
            Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Vincent Guittot <vincent.guittot@linaro.org> - 2016-06-20 11:30 +0200
              Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Peter Zijlstra <peterz@infradead.org> - 2016-06-20 12:00 +0200
                Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Vincent Guittot <vincent.guittot@linaro.org> - 2016-06-20 12:10 +0200
              Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Peter Zijlstra <peterz@infradead.org> - 2016-06-21 13:50 +0200
                Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Vincent Guittot <vincent.guittot@linaro.org> - 2016-06-21 14:40 +0200
                Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Peter Zijlstra <peterz@infradead.org> - 2016-06-21 14:50 +0200
                Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Vincent Guittot <vincent.guittot@linaro.org> - 2016-06-21 15:10 +0200
            Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Dietmar Eggemann <dietmar.eggemann@arm.com> - 2016-06-20 14:00 +0200
              Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Vincent Guittot <vincent.guittot@linaro.org> - 2016-06-20 14:40 +0200
                Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Dietmar Eggemann <dietmar.eggemann@arm.com> - 2016-06-20 17:00 +0200
                Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Peter Zijlstra <peterz@infradead.org> - 2016-06-21 10:50 +0200
                Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Yuyang Du <yuyang.du@intel.com> - 2016-06-21 14:50 +0200
                Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Vincent Guittot <vincent.guittot@linaro.org> - 2016-06-21 15:40 +0200
                Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Peter Zijlstra <peterz@infradead.org> - 2016-06-22 13:50 +0200
                Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Peter Zijlstra <peterz@infradead.org> - 2016-06-21 16:20 +0200
                Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Dietmar Eggemann <dietmar.eggemann@arm.com> - 2016-06-23 17:40 +0200
              Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Peter Zijlstra <peterz@infradead.org> - 2016-06-20 16:50 +0200
    Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Peter Zijlstra <peterz@infradead.org> - 2016-06-23 13:20 +0200
  [PATCH 2/4] sched/fair: Fix PELT integrity for new groups Peter Zijlstra <peterz@infradead.org> - 2016-06-17 14:10 +0200
    Re: [PATCH 2/4] sched/fair: Fix PELT integrity for new groups Vincent Guittot <vincent.guittot@linaro.org> - 2016-06-17 16:00 +0200
  [PATCH 3/4] sched,cgroup: Fix cpu_cgroup_fork() Peter Zijlstra <peterz@infradead.org> - 2016-06-17 14:10 +0200
    Re: [PATCH 3/4] sched,cgroup: Fix cpu_cgroup_fork() Vincent Guittot <vincent.guittot@linaro.org> - 2016-06-17 16:00 +0200
      Re: [PATCH 3/4] sched,cgroup: Fix cpu_cgroup_fork() Peter Zijlstra <peterz@infradead.org> - 2016-06-17 16:10 +0200

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