From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Peter Zijlstra <peterz@infradead.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Douglas RAILLARD <douglas.raillard@arm.com>,
linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
viresh.kumar@linaro.org, mingo@redhat.com
Subject: Re: [PATCH] sched/cpufreq: Align trace event behavior of fast switching
Date: Mon, 26 Aug 2019 11:51:17 +0200 [thread overview]
Message-ID: <cb75ae16-727e-636b-2b79-4f049259c0aa@arm.com> (raw)
In-Reply-To: <20190826094058.GP2369@hirez.programming.kicks-ass.net>
On 26/08/2019 11:40, Peter Zijlstra wrote:
> On Mon, Aug 26, 2019 at 11:10:52AM +0200, Rafael J. Wysocki wrote:
>> On Wednesday, August 7, 2019 5:33:40 PM CEST Douglas RAILLARD wrote:
>>> Fast switching path only emits an event for the CPU of interest, whereas the
>>> regular path emits an event for all the CPUs that had their frequency changed,
>>> i.e. all the CPUs sharing the same policy.
>>>
>>> With the current behavior, looking at cpu_frequency event for a given CPU that
>>> is using the fast switching path will not give the correct frequency signal.
>>>
>>> Signed-off-by: Douglas RAILLARD <douglas.raillard@arm.com>
>>> ---
>>> kernel/sched/cpufreq_schedutil.c | 7 ++++++-
>>> 1 file changed, 6 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
>>> index 1f82ab108bab..975ccc3de807 100644
>>> --- a/kernel/sched/cpufreq_schedutil.c
>>> +++ b/kernel/sched/cpufreq_schedutil.c
>>> @@ -153,6 +153,7 @@ static void sugov_fast_switch(struct sugov_policy *sg_policy, u64 time,
>>> unsigned int next_freq)
>>> {
>>> struct cpufreq_policy *policy = sg_policy->policy;
>>> + int cpu;
>>>
>>> if (!sugov_update_next_freq(sg_policy, time, next_freq))
>>> return;
>>> @@ -162,7 +163,11 @@ static void sugov_fast_switch(struct sugov_policy *sg_policy, u64 time,
>>> return;
>>>
>>> policy->cur = next_freq;
>>> - trace_cpu_frequency(next_freq, smp_processor_id());
>>> +
>>> + if (trace_cpu_frequency_enabled()) {
>>> + for_each_cpu(cpu, policy->cpus)
>>> + trace_cpu_frequency(next_freq, cpu);
>>> + }
>>> }
>>>
>>> static void sugov_deferred_update(struct sugov_policy *sg_policy, u64 time,
>>>
>>
>> Peter, any comments here?
>
> I was thinking this would be a static map and dealing with it would be
> something trivially done in post (or manually while reading), but sure,
> whatever:
>
> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
I think our EAS tooling expects the behavior of the non-fast-switching
driver (cpufreq.c cpufreq_notify_transition() CPUFREQ_POSTCHANGE). Pixel
3 is the first device with a fast-switching driver we test on.
Not sure about the extra 'if trace_cpu_frequency_enabled()' but I guess
it doesn't hurt.
next prev parent reply other threads:[~2019-08-26 9:51 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-07 15:33 [PATCH] sched/cpufreq: Align trace event behavior of fast switching Douglas RAILLARD
2019-08-07 20:40 ` Rafael J. Wysocki
2019-08-08 16:18 ` Douglas Raillard
2019-08-26 9:10 ` Rafael J. Wysocki
2019-08-26 9:40 ` Peter Zijlstra
2019-08-26 9:51 ` Dietmar Eggemann [this message]
2019-08-26 11:24 ` Peter Zijlstra
2019-08-26 12:12 ` Dietmar Eggemann
2019-08-28 9:44 ` Rafael J. Wysocki
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