From: Sudeep Holla <sudeep.holla@arm.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linux-pm@vger.kernel.org, rjw@rjwysocki.net,
linux-kernel@vger.kernel.org, cristian.marussi@arm.com,
Sudeep Holla <sudeep.holla@arm.com>,
Lukasz Luba <lukasz.luba@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 0/4] CPUFreq statistics retrieved by drivers
Date: Thu, 30 Jul 2020 10:10:14 +0100 [thread overview]
Message-ID: <20200730091014.GA13158@bogus> (raw)
In-Reply-To: <20200730085333.qubrsv7ufqninihd@vireshk-mac-ubuntu>
On Thu, Jul 30, 2020 at 02:23:33PM +0530, Viresh Kumar wrote:
> On 29-07-20, 16:12, Lukasz Luba wrote:
> > The existing CPUFreq framework does not tracks the statistics when the
> > 'fast switch' is used or when firmware changes the frequency independently
> > due to e.g. thermal reasons. However, the firmware might track the frequency
> > changes and expose this to the kernel.
> >
> > This patch set aims to introduce CPUfreq statistics gathered by firmware
> > and retrieved by CPUFreq driver. It would require a new API functions
> > in the CPUFreq, which allows to poke drivers to get these stats.
> >
> > The needed CPUFreq infrastructure is in patch 1/4, patch 2/4 extends
> > ARM SCMI protocol layer, patches 3/4, 4/4 modify ARM SCMI CPUFreq driver.
>
> Are you doing this for the fast switch case or because your platform
> actually runs at frequencies which may be different from what cpufreq
> core has requested ?
>
I think so.
> I am also not sure what these tables should represent, what the
> cpufreq core has decided for the CPUs or the frequencies we actually
> run at, as these two can be very different for example if the hardware
> runs at frequencies which don't match exactly to what is there in the
> freq table. I believe these are rather to show what cpufreq and its
> governors are doing with the CPUs.
>
Exactly, I raised similar point in internal discussion and asked Lukasz
to take up the same on the list. I assume it was always what cpufreq
requested rather than what was delivered. So will we break the userspace
ABI if we change that is the main question.
> Over that I would like the userspace stats to work exactly as the way
> they work right now, i.e. capture all transitions from one freq to
> other, not just time-in-state. Also resetting of the stats from
> userspace for example. All allocation and printing of the data must be
> done from stats core, the only thing which the driver would do at the
> end is updating the stats structure and nothing more. Instead of
> reading all stats from the firmware, it will be much easier if you can
> just get the information from the firmware whenever there is a
> frequency switch and then we can update the stats the way it is done
> right now. And that would be simple.
>
Good point, but notifications may not be lightweight. If that is no good,
alternatively, I suggested to keep these firmware stats in a separate
debugfs. Thoughts ?
--
Regards,
Sudeep
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next prev parent reply other threads:[~2020-07-30 9:11 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-29 15:12 [PATCH 0/4] CPUFreq statistics retrieved by drivers Lukasz Luba
2020-07-29 15:12 ` [PATCH 1/4] cpufreq: Add support for statistics read from drivers Lukasz Luba
2020-07-29 15:12 ` [PATCH 2/4] scmi: perf: Extend protocol to support performance statistics Lukasz Luba
2020-07-31 1:50 ` kernel test robot
2020-07-31 15:15 ` Cristian Marussi
2020-08-04 11:10 ` Lukasz Luba
2020-07-29 15:12 ` [PATCH 3/4] cpufreq: scmi: Move scmi_cpufreq_driver structure to the top Lukasz Luba
2020-07-29 15:12 ` [PATCH 4/4] cpufreq: scmi: Read statistics from FW shared memory Lukasz Luba
2020-07-30 8:53 ` [PATCH 0/4] CPUFreq statistics retrieved by drivers Viresh Kumar
2020-07-30 9:10 ` Sudeep Holla [this message]
2020-07-30 9:36 ` Lukasz Luba
2020-07-31 15:56 ` Sudeep Holla
2020-08-04 17:19 ` Florian Fainelli
2020-08-05 12:36 ` Sudeep Holla
2020-08-04 5:35 ` Viresh Kumar
2020-08-04 10:29 ` Lukasz Luba
2020-08-04 10:38 ` Viresh Kumar
2020-08-04 10:44 ` Lukasz Luba
2020-09-02 7:26 ` Viresh Kumar
2020-08-04 17:27 ` Florian Fainelli
2020-08-05 11:04 ` Lukasz Luba
2020-08-05 13:04 ` Viresh Kumar
2020-08-05 16:03 ` Sudeep Holla
2020-08-05 17:33 ` Florian Fainelli
2020-08-06 13:37 ` Sudeep Holla
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