From: Patrick Bellasi <patrick.bellasi@arm.com>
To: Juri Lelli <juri.lelli@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
Viresh Kumar <viresh.kumar@linaro.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Todd Kjos <tkjos@android.com>, Joel Fernandes <joelaf@google.com>
Subject: Re: [PATCH v3 1/6] cpufreq: schedutil: reset sg_cpus's flags at IDLE enter
Date: Thu, 30 Nov 2017 15:41:11 +0000 [thread overview]
Message-ID: <20171130154111.GC31247@e110439-lin> (raw)
In-Reply-To: <20171130131222.GA9903@localhost.localdomain>
On 30-Nov 14:12, Juri Lelli wrote:
> Hi,
>
> On 30/11/17 11:47, Patrick Bellasi wrote:
>
> [...]
>
> > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> > index 2f52ec0f1539..67339ccb5595 100644
> > --- a/kernel/sched/cpufreq_schedutil.c
> > +++ b/kernel/sched/cpufreq_schedutil.c
> > @@ -347,6 +347,12 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
> >
> > sg_cpu->util = util;
> > sg_cpu->max = max;
> > +
> > + /* CPU is entering IDLE, reset flags without triggering an update */
> > + if (unlikely(flags & SCHED_CPUFREQ_IDLE)) {
> > + sg_cpu->flags = 0;
> > + goto done;
> > + }
>
> Looks good for now. I'm just thinking that we will happen for DL, as a
> CPU that still "has" a sleeping task is not going to be really idle
> until the 0-lag time.
AFAIU, for the time being, DL already cannot really rely on this flag
for its behaviors to be correct. Indeed, flags are reset as soon as
a FAIR task wakes up and it's enqueued.
Only once your DL integration patches are in, we do not depends on
flags anymore since DL will report a ceratain utilization up to the
0-lag time, isn't it?
If that's the case, I would say that the flags will be used only to
jump to the max OPP for RT tasks. Thus, this patch should still be valid.
> I guess we could move this at that point in time?
Not sure what you mean here. Right now the new SCHED_CPUFREQ_IDLE flag
is notified only by idle tasks. That's the only code path where we are
sure the CPU is entering IDLE.
> > sg_cpu->flags = flags;
> >
> > sugov_set_iowait_boost(sg_cpu, time, flags);
> > @@ -361,6 +367,7 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
> > sugov_update_commit(sg_policy, time, next_f);
> > }
> >
> > +done:
> > raw_spin_unlock(&sg_policy->update_lock);
> > }
> >
> > diff --git a/kernel/sched/idle_task.c b/kernel/sched/idle_task.c
> > index d518664cce4f..6e8ae2aa7a13 100644
> > --- a/kernel/sched/idle_task.c
> > +++ b/kernel/sched/idle_task.c
> > @@ -30,6 +30,10 @@ pick_next_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf
> > put_prev_task(rq, prev);
> > update_idle_core(rq);
> > schedstat_inc(rq->sched_goidle);
> > +
> > + /* kick cpufreq (see the comment in kernel/sched/sched.h). */
> > + cpufreq_update_util(rq, SCHED_CPUFREQ_IDLE);
>
> Don't know if it make things any cleaner, but you could add to the
> comment that we don't actually trigger a frequency update with this
> call.
Right, will add on next posting.
> Best,
>
> Juri
Cheers Patrick
--
#include <best/regards.h>
Patrick Bellasi
next prev parent reply other threads:[~2017-11-30 15:41 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-30 11:47 [PATCH v3 0/6] cpufreq: schedutil: fixes for flags updates Patrick Bellasi
2017-11-30 11:47 ` [PATCH v3 1/6] cpufreq: schedutil: reset sg_cpus's flags at IDLE enter Patrick Bellasi
2017-11-30 13:12 ` Juri Lelli
2017-11-30 15:41 ` Patrick Bellasi [this message]
2017-11-30 16:02 ` Juri Lelli
2017-11-30 16:19 ` Patrick Bellasi
2017-11-30 16:45 ` Juri Lelli
2017-12-07 5:01 ` Viresh Kumar
2017-12-07 12:45 ` Patrick Bellasi
2017-12-07 15:55 ` Dietmar Eggemann
2017-12-12 11:37 ` Viresh Kumar
2017-12-12 13:38 ` Juri Lelli
2017-12-12 14:40 ` Viresh Kumar
2017-12-12 14:56 ` Juri Lelli
2017-12-12 15:18 ` Patrick Bellasi
2017-12-12 15:16 ` Patrick Bellasi
2017-12-13 9:06 ` Viresh Kumar
2017-12-20 14:33 ` Peter Zijlstra
2017-12-20 14:51 ` Patrick Bellasi
2017-11-30 11:47 ` [PATCH v3 2/6] cpufreq: schedutil: ensure max frequency while running RT/DL tasks Patrick Bellasi
2017-11-30 13:17 ` Juri Lelli
2017-11-30 15:45 ` Patrick Bellasi
2017-11-30 16:03 ` Juri Lelli
2017-12-07 5:05 ` Viresh Kumar
2017-12-07 14:18 ` Patrick Bellasi
2017-11-30 11:47 ` [PATCH v3 3/6] cpufreq: schedutil: update CFS util only if used Patrick Bellasi
2017-11-30 13:22 ` Juri Lelli
2017-11-30 15:57 ` Patrick Bellasi
2017-12-07 5:15 ` Viresh Kumar
2017-12-07 14:19 ` Patrick Bellasi
2017-12-14 4:45 ` Viresh Kumar
2017-11-30 11:47 ` [PATCH v3 4/6] sched/rt: fast switch to maximum frequency when RT tasks are scheduled Patrick Bellasi
2017-11-30 13:28 ` Juri Lelli
2017-12-06 9:39 ` Vincent Guittot
2017-12-06 11:38 ` Patrick Bellasi
2017-12-06 12:36 ` Vincent Guittot
2017-11-30 11:47 ` [PATCH v3 5/6] cpufreq: schedutil: relax rate-limiting while running RT/DL tasks Patrick Bellasi
2017-11-30 13:36 ` Juri Lelli
2017-11-30 15:54 ` Patrick Bellasi
2017-11-30 16:06 ` Juri Lelli
2017-11-30 11:47 ` [PATCH v3 6/6] cpufreq: schedutil: ignore sugov kthreads Patrick Bellasi
2017-11-30 13:41 ` Juri Lelli
2017-11-30 16:02 ` Patrick Bellasi
2017-11-30 16:12 ` Juri Lelli
2017-11-30 16:42 ` Patrick Bellasi
2017-12-07 9:24 ` Viresh Kumar
2017-12-07 15:47 ` Patrick Bellasi
2017-12-20 15:30 ` [PATCH v3 0/6] cpufreq: schedutil: fixes for flags updates Peter Zijlstra
2017-12-20 15:43 ` Peter Zijlstra
2017-12-21 9:15 ` Viresh Kumar
2017-12-21 10:25 ` Peter Zijlstra
2017-12-21 10:30 ` Viresh Kumar
2017-12-21 10:39 ` Peter Zijlstra
2017-12-21 10:43 ` Viresh Kumar
2017-12-22 8:30 ` Peter Zijlstra
2017-12-20 15:56 ` Peter Zijlstra
2017-12-31 9:43 ` Claudio Scordino
2018-01-02 13:31 ` Claudio Scordino
2017-12-20 17:38 ` Juri Lelli
2017-12-20 18:16 ` Peter Zijlstra
2017-12-22 10:06 ` Peter Zijlstra
2017-12-22 11:02 ` Patrick Bellasi
2017-12-22 11:46 ` Peter Zijlstra
2017-12-22 12:07 ` Juri Lelli
2017-12-22 12:14 ` Patrick Bellasi
2017-12-22 12:22 ` Peter Zijlstra
2017-12-22 12:07 ` Patrick Bellasi
2017-12-22 12:19 ` Peter Zijlstra
2017-12-22 12:27 ` Juri Lelli
2017-12-22 12:38 ` Patrick Bellasi
2017-12-22 12:43 ` Juri Lelli
2017-12-22 12:50 ` Patrick Bellasi
2017-12-22 13:01 ` Juri Lelli
2017-12-22 12:10 ` Peter Zijlstra
2017-12-22 12:25 ` Patrick Bellasi
2017-12-21 7:34 ` Viresh Kumar
2018-02-06 10:55 ` Claudio Scordino
2018-02-06 15:43 ` Patrick Bellasi
[not found] ` <68afaf84-893e-6770-b9f1-619cd2b6dc9c@evidence.eu.com>
2018-02-06 18:36 ` Patrick Bellasi
2018-02-08 16:14 ` Claudio Scordino
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