From: Vikram Mulukutla <markivx@codeaurora.org>
To: Patrick Bellasi <patrick.bellasi@arm.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>,
Juri Lelli <juri.lelli@arm.com>,
Joel Fernandes <joelaf@google.com>,
Andres Oportus <andresoportus@google.com>,
Todd Kjos <tkjos@android.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
linux-kernel-owner@vger.kernel.org
Subject: Re: [PATCH v2 4/6] cpufreq: schedutil: update CFS util only if used
Date: Thu, 06 Jul 2017 23:44:09 -0700 [thread overview]
Message-ID: <c04bdad3354a0ee0aabe63fe813fdaf5@codeaurora.org> (raw)
In-Reply-To: <1499189651-18797-5-git-send-email-patrick.bellasi@arm.com>
On 2017-07-04 10:34, Patrick Bellasi wrote:
> Currently the utilization of the FAIR class is collected before locking
> the policy. Although that should not be a big issue for most cases, we
> also don't really know how much latency there can be between the
> utilization reading and its usage.
>
> Let's get the FAIR utilization right before its usage to be better in
> sync with the current status of a CPU.
>
> Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Cc: Viresh Kumar <viresh.kumar@linaro.org>
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-pm@vger.kernel.org
> ---
> kernel/sched/cpufreq_schedutil.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/kernel/sched/cpufreq_schedutil.c
> b/kernel/sched/cpufreq_schedutil.c
> index 98704d8..df433f1 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -308,10 +308,9 @@ static void sugov_update_shared(struct
> update_util_data *hook, u64 time,
> if (unlikely(current == sg_policy->thread))
> return;
>
> - sugov_get_util(&util, &max);
> -
> raw_spin_lock(&sg_policy->update_lock);
>
> + sugov_get_util(&util, &max);
> sg_cpu->util = util;
> sg_cpu->max = max;
Given that the utilization update hooks are called with the per-cpu rq
lock held (for all classes), I don't think PELT utilization can change
throughout the lifetime of the cpufreq_update_{util,this_cpu} call? Even
with Viresh's remote cpu callback series we'd still have to hold the rq
lock across cpufreq_update_util.. what can change today is 'max'
(arch_scale_cpu_capacity) when a cpufreq policy is shared, so the patch
is still needed for that reason I think?
Thanks,
Vikram
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
next prev parent reply other threads:[~2017-07-07 6:44 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-04 17:34 [PATCH v2 0/6] cpufreq: schedutil: fixes for flags updates Patrick Bellasi
2017-07-04 17:34 ` [PATCH v2 1/6] cpufreq: schedutil: ignore sugov kthreads Patrick Bellasi
2017-07-05 5:00 ` Viresh Kumar
2017-07-05 11:38 ` Patrick Bellasi
2017-07-06 4:50 ` Viresh Kumar
2017-07-06 22:18 ` Rafael J. Wysocki
2017-07-11 19:08 ` Saravana Kannan
2017-07-04 17:34 ` [PATCH v2 2/6] cpufreq: schedutil: reset sg_cpus's flags at IDLE enter Patrick Bellasi
2017-07-05 4:50 ` Viresh Kumar
2017-07-05 13:04 ` Patrick Bellasi
2017-07-06 5:46 ` Viresh Kumar
2017-07-07 4:43 ` Joel Fernandes
2017-07-07 10:17 ` Juri Lelli
2017-07-11 19:16 ` Saravana Kannan
2017-07-04 17:34 ` [PATCH v2 3/6] cpufreq: schedutil: ensure max frequency while running RT/DL tasks Patrick Bellasi
2017-07-05 6:01 ` Viresh Kumar
2017-07-05 13:41 ` Patrick Bellasi
2017-07-06 5:56 ` Viresh Kumar
2017-07-07 5:26 ` Joel Fernandes
2017-07-04 17:34 ` [PATCH v2 4/6] cpufreq: schedutil: update CFS util only if used Patrick Bellasi
2017-07-07 5:58 ` Joel Fernandes
2017-07-07 6:44 ` Vikram Mulukutla [this message]
2017-07-08 6:14 ` Joel Fernandes
2017-07-10 17:49 ` Vikram Mulukutla
2017-07-11 5:19 ` Joel Fernandes
2017-07-04 17:34 ` [PATCH v2 5/6] sched/rt: fast switch to maximum frequency when RT tasks are scheduled Patrick Bellasi
2017-07-04 17:34 ` [PATCH v2 6/6] cpufreq: schedutil: relax rate-limiting while running RT/DL tasks Patrick Bellasi
2017-07-06 22:26 ` [PATCH v2 0/6] cpufreq: schedutil: fixes for flags updates Rafael J. Wysocki
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