linux-kernel - Re: [PATCH v5 2/2] sched/fair: update scale invariance of PELT

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Date:   Mon, 5 Nov 2018 08:59:42 +0100
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Morten Rasmussen <Morten.Rasmussen@....com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Paul Turner <pjt@...gle.com>, Ben Segall <bsegall@...gle.com>,
        Thara Gopinath <thara.gopinath@...aro.org>,
        pkondeti@...eaurora.org
Subject: Re: [PATCH v5 2/2] sched/fair: update scale invariance of PELT

On Thu, 1 Nov 2018 at 10:38, Dietmar Eggemann <dietmar.eggemann@....com> wrote:
>
> On 10/31/18 10:18 AM, Vincent Guittot wrote:
> > Hi Dietmar,
> >
> > On Wed, 31 Oct 2018 at 08:20, Dietmar Eggemann <dietmar.eggemann@....com> wrote:
> >>
> >> On 10/26/18 6:11 PM, Vincent Guittot wrote:
> >>
> >> [...]
> >>
> >>>    static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
> >>>    static unsigned long task_h_load(struct task_struct *p);
> >>> @@ -764,7 +763,7 @@ void post_init_entity_util_avg(struct sched_entity *se)
> >>>                         * such that the next switched_to_fair() has the
> >>>                         * expected state.
> >>>                         */
> >>> -                     se->avg.last_update_time = cfs_rq_clock_task(cfs_rq);
> >>> +                     se->avg.last_update_time = cfs_rq_clock_pelt(cfs_rq);
> >>>                        return;
> >>>                }
> >>>        }
> >>
> >> There is this 1/cpu scaling of se->avg.util_sum (running_sum) in
> >> update_tg_cfs_runnable() so it can be used to calculate
> >> se->avg.runnable_load_sum (runnable_sum). I guess with your approach
> >> this should be removed.
> >
> > Yes good catch
>
> Another thing, since you do not need the cpu parameter in
> accumulate_sum() anymore, you could also get rid of it in
> ___update_load_sum() and further in __update_load_avg_blocked_se(),
> __update_load_avg_cfs_rq() and __update_load_avg_se().

yes, I have to clean interface from reference to cpu

>
> Nitpick: The function header of update_cfs_rq_load_avg() mentions '@now:
> current time, as per cfs_rq_clock_task()' ... should mention
> cfs_rq_clock_pelt() instead.

ok

>
> [...]