linux-kernel - Re: [PATCH] psi : calc cfs task memstall time more precisely

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Date:   Wed, 15 Sep 2021 10:40:32 +0800
From:   Zhaoyang Huang <huangzhaoyang@...il.com>
To:     Johannes Weiner <hannes@...xchg.org>
Cc:     Zhaoyang Huang <zhaoyang.huang@...soc.com>,
        "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, xuewen.yan@...soc.com,
        Ke Wang <ke.wang@...soc.com>
Subject: Re: [PATCH] psi : calc cfs task memstall time more precisely

Any comments on this patch?

On Mon, Sep 13, 2021 at 9:11 AM Zhaoyang Huang <huangzhaoyang@...il.com> wrote:
>
> Sorry for the confusion. Actually, it is a new design which has taken
> previous advice into consideration. I agree that part of the off cpu
> time among the memstall time should be counted in, whereas, the
> preempted time by high priority tasks should NOT be, including
> RT,DEADLINE,IRQS time on cfs task.
>
> On Fri, Sep 10, 2021 at 9:16 PM Johannes Weiner <hannes@...xchg.org> wrote:
> >
> > Please don't send new revisions without replying to previous feedback.
> >
> > On Fri, Sep 10, 2021 at 03:54:46PM +0800, Huangzhaoyang wrote:
> > > From: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> > >
> > > cfs task's memstall time is counted as simple as exit - entry so far, which
> > > ignore the preempted time by rt, dl and irq time. Eliminating them by calc the
> > > time growth via the proportion of cfs_rq's utilization on the whole rq.
> > >
> > > eg.
> > > Here is the scenario which this commit want to fix, that is the rt and irq consume
> > > some utilization of the whole rq. This scenario could be typical in a core
> > > which is assigned to deal with all irqs. Furthermore, the rt task used to run on
> > > little core under EAS.
> > >
> > > Binder:305_3-314    [002] d..1   257.880195: psi_memtime_fixup: original:30616,adjusted:25951,se:89,cfs:353,rt:139,dl:0,irq:18
> > > droid.phone-1525    [001] d..1   265.145492: psi_memtime_fixup: original:61616,adjusted:53492,se:55,cfs:225,rt:121,dl:0,irq:15
> > >
> > > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> > > ---
> > >  kernel/sched/psi.c | 20 +++++++++++++++++++-
> > >  1 file changed, 19 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
> > > index cc25a3c..754a836 100644
> > > --- a/kernel/sched/psi.c
> > > +++ b/kernel/sched/psi.c
> > > @@ -182,6 +182,8 @@ struct psi_group psi_system = {
> > >
> > >  static void psi_avgs_work(struct work_struct *work);
> > >
> > > +static unsigned long psi_memtime_fixup(u32 growth);
> > > +
> > >  static void group_init(struct psi_group *group)
> > >  {
> > >       int cpu;
> > > @@ -492,6 +494,21 @@ static u64 window_update(struct psi_window *win, u64 now, u64 value)
> > >       return growth;
> > >  }
> > >
> > > +static unsigned long psi_memtime_fixup(u32 growth)
> > > +{
> > > +     struct rq *rq = task_rq(current);
> > > +     unsigned long growth_fixed = (unsigned long)growth;
> > > +
> > > +     if (!(current->policy == SCHED_NORMAL || current->policy == SCHED_BATCH))
> > > +             return growth_fixed;
> > > +
> > > +     if (current->in_memstall)
> > > +             growth_fixed = div64_ul((1024 - rq->avg_rt.util_avg - rq->avg_dl.util_avg
> > > +                                     - rq->avg_irq.util_avg + 1) * growth, 1024);
> > > +
> > > +     return growth_fixed;
> > > +}
> > > +
> > >  static void init_triggers(struct psi_group *group, u64 now)
> > >  {
> > >       struct psi_trigger *t;
> > > @@ -658,6 +675,7 @@ static void record_times(struct psi_group_cpu *groupc, u64 now)
> > >       }
> > >
> > >       if (groupc->state_mask & (1 << PSI_MEM_SOME)) {
> > > +             delta = psi_memtime_fixup(delta);
> > >               groupc->times[PSI_MEM_SOME] += delta;
> > >               if (groupc->state_mask & (1 << PSI_MEM_FULL))
> > >                       groupc->times[PSI_MEM_FULL] += delta;
> > > @@ -928,8 +946,8 @@ void psi_memstall_leave(unsigned long *flags)
> > >        */
> > >       rq = this_rq_lock_irq(&rf);
> > >
> > > -     current->in_memstall = 0;
> > >       psi_task_change(current, TSK_MEMSTALL, 0);
> > > +     current->in_memstall = 0;
> > >
> > >       rq_unlock_irq(rq, &rf);
> > >  }
> > > --
> > > 1.9.1
> > >