From: Juri Lelli <juri.lelli@arm.com>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Viresh Kumar <viresh.kumar@linaro.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux PM <linux-pm@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Vincent Guittot <vincent.guittot@linaro.org>,
Steven Rostedt <rostedt@goodmis.org>,
Luca Abeni <luca.abeni@santannapisa.it>,
claudio@evidence.eu.com, tommaso.cucinotta@santannapisa.it,
bristot@redhat.com, mathieu.poirier@linaro.org,
Todd Kjos <tkjos@android.com>, Joel Fernandes <joelaf@google.com>,
Andres Oportus <andresoportus@google.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Patrick Bellasi <patrick.bellasi@arm.com>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [RFD PATCH 4/5] sched/cpufreq_schedutil: always consider all CPUs when deciding next freq
Date: Fri, 31 Mar 2017 08:31:26 +0100 [thread overview]
Message-ID: <20170331073126.GK19929@e106622-lin> (raw)
In-Reply-To: <CAJZ5v0jyHkVg80Uk5rh4Ax1wqFk=i+nbYEUfakDNrhu8zLnRzg@mail.gmail.com>
On 30/03/17 22:13, Rafael J. Wysocki wrote:
> On Thu, Mar 30, 2017 at 10:58 AM, Juri Lelli <juri.lelli@arm.com> wrote:
> > Hi,
>
> Hi,
>
> > On 30/03/17 00:41, Rafael J. Wysocki wrote:
> >> On Friday, March 24, 2017 02:08:59 PM Juri Lelli wrote:
> >> > No assumption can be made upon the rate at which frequency updates get
> >> > triggered, as there are scheduling policies (like SCHED_DEADLINE) which
> >> > don't trigger them so frequently.
> >> >
> >> > Remove such assumption from the code.
> >>
> >> But the util/max values for idle CPUs may be stale, no?
> >>
> >
> > Right, that might be a problem. A proper solution I think would be to
> > remotely update such values for idle CPUs, and I believe Vincent is
> > working on a patch for that.
> >
> > As mid-term workarounds, changing a bit the current one, come to my
> > mind:
> >
> > - consider TICK_NSEC (continue) only when SCHED_CPUFREQ_DL is not set
> > - remove CFS contribution (without triggering a freq update) when a CPU
> > enters IDLE; this might not work well, though, as we probably want
> > to keep in blocked util contribution for a bit
> >
> > What you think is the way to go?
>
> Well, do we want SCHED_DEADLINE util contribution to be there even for
> idle CPUs?
>
DEADLINE util contribution is removed, even if the CPU is idle, by the
reclaiming mechanism when we know (applying GRUB algorithm rules [1])
that it can't be used anymore by a task (roughly speaking). So, we
shouldn't have this problem in the DEADLINE case.
[1] https://marc.info/?l=linux-kernel&m=149029880524038
next prev parent reply other threads:[~2017-03-31 7:31 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-24 14:08 [RFD PATCH 0/5] SCHED_DEADLINE freq/cpu invariance and OPP selection Juri Lelli
2017-03-24 14:08 ` [RFD PATCH 1/5] sched/cpufreq_schedutil: make use of DEADLINE utilization signal Juri Lelli
2017-03-24 14:08 ` [RFD PATCH 2/5] sched/deadline: move cpu frequency selection triggering points Juri Lelli
2017-03-24 14:08 ` [RFD PATCH 3/5] sched/cpufreq_schedutil: make worker kthread be SCHED_DEADLINE Juri Lelli
2017-03-27 16:50 ` Peter Zijlstra
2017-03-27 17:01 ` Juri Lelli
2017-03-27 17:05 ` Rafael J. Wysocki
2017-03-27 17:13 ` Juri Lelli
2017-03-27 17:37 ` Rafael J. Wysocki
2017-03-27 18:09 ` Mark Brown
2017-03-30 15:50 ` Vikram Mulukutla
2017-03-30 20:22 ` Rafael J. Wysocki
2017-03-31 7:26 ` Juri Lelli
2017-03-27 18:05 ` Mark Brown
2017-03-28 9:29 ` Vincent Guittot
2017-03-28 10:20 ` Peter Zijlstra
2017-03-24 14:08 ` [RFD PATCH 4/5] sched/cpufreq_schedutil: always consider all CPUs when deciding next freq Juri Lelli
2017-03-29 22:41 ` Rafael J. Wysocki
2017-03-30 8:58 ` Juri Lelli
2017-03-30 13:21 ` Vincent Guittot
2017-03-30 20:13 ` Rafael J. Wysocki
2017-03-31 7:31 ` Juri Lelli [this message]
2017-03-31 9:03 ` Rafael J. Wysocki
2017-03-31 9:16 ` Juri Lelli
2017-03-24 14:09 ` [RFD PATCH 5/5] sched/deadline: make bandwidth enforcement scale-invariant Juri Lelli
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