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 10:16:30 +0100 [thread overview]
Message-ID: <20170331091630.GP19929@e106622-lin> (raw)
In-Reply-To: <CAJZ5v0jgpLrZ1GNWSqZACrUT0NLQzo1Kktdo5wYbmaZ-vM=NcQ@mail.gmail.com>
On 31/03/17 11:03, Rafael J. Wysocki wrote:
> On Fri, Mar 31, 2017 at 9:31 AM, Juri Lelli <juri.lelli@arm.com> wrote:
> > 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
>
> OK
>
> Why don't you store the contributions from DL and CFS separately, then
> (say, as util_dl, util_cfs, respectively) and only discard the CFS one
> if delta_ns > TICK_NSEC?
Sure, this should work as well. I'll try this approach for next version.
Thanks,
- Juri
next prev parent reply other threads:[~2017-03-31 9:16 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
2017-03-31 9:03 ` Rafael J. Wysocki
2017-03-31 9:16 ` Juri Lelli [this message]
2017-03-24 14:09 ` [RFD PATCH 5/5] sched/deadline: make bandwidth enforcement scale-invariant Juri Lelli
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