From: Lukasz Luba <lukasz.luba@arm.com>
To: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Linux PM <linux-pm@vger.kernel.org>,
amit daniel kachhap <amit.kachhap@gmail.com>,
Viresh Kumar <viresh.kumar@linaro.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Amit Kucheria <amitk@kernel.org>, Zhang Rui <rui.zhang@intel.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Pierre.Gondois@arm.com, Stephen Boyd <swboyd@chromium.org>,
Rajendra Nayak <rnayak@codeaurora.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
Doug Anderson <dianders@chromium.org>,
Matthias Kaehlcke <mka@chromium.org>
Subject: Re: [PATCH 1/2] thermal: cooling: Check Energy Model type in cpufreq_cooling and devfreq_cooling
Date: Thu, 17 Feb 2022 12:11:27 +0000 [thread overview]
Message-ID: <97ecc29b-13a9-fa15-4e88-21c8612ebb7f@arm.com> (raw)
In-Reply-To: <53bc13ca-998f-ff83-d9f7-9a83d35b24fd@linaro.org>
On 2/17/22 11:28 AM, Daniel Lezcano wrote:
> On 17/02/2022 11:47, Lukasz Luba wrote:
>> Hi Daniel,
>>
>> On 2/17/22 10:10 AM, Daniel Lezcano wrote:
>>> On 16/02/2022 18:33, Doug Anderson wrote:
>>>> Hi,
>>>>
>>>> On Wed, Feb 16, 2022 at 7:35 AM Lukasz Luba <lukasz.luba@arm.com>
>>>> wrote:
>>>>>
>>>>> Hi Matthias,
>>>>>
>>>>> On 2/9/22 10:17 PM, Matthias Kaehlcke wrote:
>>>>>> On Wed, Feb 09, 2022 at 11:16:36AM +0000, Lukasz Luba wrote:
>>>>>>>
>>>>>>>
>>>>>>> On 2/8/22 5:25 PM, Matthias Kaehlcke wrote:
>>>>>>>> On Tue, Feb 08, 2022 at 09:32:28AM +0000, Lukasz Luba wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>
>>>>> [snip]
>>>>>
>>>>>>>>> Could you point me to those devices please?
>>>>>>>>
>>>>>>>> arch/arm64/boot/dts/qcom/sc7180-trogdor-*
>>>>>>>>
>>>>>>>> Though as per above they shouldn't be impacted by your change,
>>>>>>>> since the
>>>>>>>> CPUs always pretend to use milli-Watts.
>>>>>>>>
>>>>>>>> [skipped some questions/answers since sc7180 isn't actually
>>>>>>>> impacted by
>>>>>>>> the change]
>>>>>>>
>>>>>>> Thank you Matthias. I will investigate your setup to get better
>>>>>>> understanding.
>>>>>>
>>>>>> Thanks!
>>>>>>
>>>>>
>>>>> I've checked those DT files and related code.
>>>>> As you already said, this patch is safe for them.
>>>>> So we can apply it IMO.
>>>>>
>>>>>
>>>>> -------------Off-topic------------------
>>>>> Not in $subject comments:
>>>>>
>>>>> AFAICS based on two files which define thermal zones:
>>>>> sc7180-trogdor-homestar.dtsi
>>>>> sc7180-trogdor-coachz.dtsi
>>>>>
>>>>> only the 'big' cores are used as cooling devices in the
>>>>> 'skin_temp_thermal' - the CPU6 and CPU7.
>>>>>
>>>>> I assume you don't want to model at all the power usage
>>>>> from the Little cluster (which is quite big: 6 CPUs), do you?
>>>>> I can see that the Little CPUs have small dyn-power-coeff
>>>>> ~30% of the big and lower max freq, but still might be worth
>>>>> to add them to IPA. You might give them more 'weight', to
>>>>> make sure they receive more power during power split.
>>>>>
>>>>> You also don't have GPU cooling device in that thermal zone.
>>>>> Based on my experience if your GPU is a power hungry one,
>>>>> e.g. 2-4Watts, you might get better results when you model
>>>>> this 'hot' device (which impacts your temp sensor reported value).
>>>>
>>>> I think the two boards you point at (homestar and coachz) are just the
>>>> two that override the default defined in the SoC dtsi file. If you
>>>> look in sc7180.dtsi you'll see 'gpuss1-thermal' which has a cooling
>>>> map. You can also see the cooling maps for the littles.
>>>>
>>>> I guess we don't have a `dynamic-power-coefficient` for the GPU,
>>>> though? Seems like we should, but I haven't dug through all the code
>>>> here...
>>>
>>> The dynamic-power-coefficient is available for OPPs which includes
>>> CPUfreq and devfreq. As the GPU is managed by devfreq, setting the
>>> dynamic-power-coefficient makes the energy model available for it.
>>>
>>> However, the OPPs must define the frequency and the voltage. That is
>>> the case for most platforms except on QCom platform.
>>>
>>> That may not be specified as it uses a frequency index and the
>>> hardware does the voltage change in our back. The QCom cpufreq
>>> backend get the voltage table from a register (or whatever) and
>>> completes the voltage values for the OPPs, thus adding the
>>> information which is missing in the device tree. The energy model can
>>> then initializes itself and allows the usage of the Energy Aware
>>> Scheduler.
>>>
>>> However this piece of code is missing for the GPU part.
>>>
>>
>> Thank you for joining the discussion. I don't know about that Qcom
>> GPU voltage information is missing.
>>
>> If the voltage is not available (only the frequencies), there is
>> another way. There is an 'advanced' EM which uses registration function:
>> em_dev_register_perf_domain(). It uses a local driver callback to get
>> power for each found frequency. It has benefit because there is no
>> restriction to 'fit' into the math formula, instead just avg power
>> values can be feed into EM. It's called 'advanced' EM [1].
>>
>> Now we hit (again) the DT & EM issue (it's an old one, IIRC Morten
>> was proposing from ~2014 this upstream, but EAS wasn't merged back
>> then):
>> where to store these power-freq values, which are then used by the
>> callback.
>
> Why not make it more generic and replace the frequency by a performance
> index, so it can be used by any kind of perf limiter?
For that DT array, yes, it can be an index, so effectively it could be
a simple 1d array.
something like:
msm_gpu_energy_model: msm-gpu-energy-model {
compatible = "energy-model"
/* Values are sorted micro-Watts which correspond to each OPP
or performance state. The total amount of them must match
number of OPPs. */
power-microwatt = <100000>,
<230000>,
<380000>,
<600000>;
};
then in gpu node instead of having 'dynamic-power-coefficient',
which is useless because voltage is missing, we would have
'energy-model', like:
energy-model = <&msm_gpu_energy_model>;
If you agree to continue this topic. I will send an RFC so we could
further discuss this idea. This $subject doesn't fit well.
Thank you again for your feedback Daniel!
next prev parent reply other threads:[~2022-02-17 12:11 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-07 7:30 [PATCH 0/2] Ignore Energy Model with abstract scale in IPA and DTPM Lukasz Luba
2022-02-07 7:30 ` [PATCH 1/2] thermal: cooling: Check Energy Model type in cpufreq_cooling and devfreq_cooling Lukasz Luba
2022-02-08 0:50 ` Matthias Kaehlcke
2022-02-08 9:32 ` Lukasz Luba
2022-02-08 17:25 ` Matthias Kaehlcke
2022-02-09 11:16 ` Lukasz Luba
2022-02-09 22:17 ` Matthias Kaehlcke
2022-02-16 15:35 ` Lukasz Luba
2022-02-16 17:33 ` Doug Anderson
2022-02-16 22:13 ` Matthias Kaehlcke
2022-02-16 22:43 ` Lukasz Luba
2022-02-17 0:26 ` Matthias Kaehlcke
2022-02-17 10:15 ` Daniel Lezcano
2022-02-17 9:59 ` Daniel Lezcano
2022-02-17 10:10 ` Daniel Lezcano
2022-02-17 10:47 ` Lukasz Luba
2022-02-17 11:28 ` Daniel Lezcano
2022-02-17 12:11 ` Lukasz Luba [this message]
2022-02-17 12:33 ` Daniel Lezcano
2022-02-17 12:37 ` Lukasz Luba
2022-02-17 16:46 ` Matthias Kaehlcke
2022-02-17 16:37 ` Doug Anderson
2022-02-17 17:14 ` Matthias Kaehlcke
2022-02-17 18:05 ` Lukasz Luba
2022-02-17 18:27 ` Daniel Lezcano
2022-02-16 17:21 ` Doug Anderson
2022-02-16 23:28 ` Lukasz Luba
2022-02-17 16:50 ` Doug Anderson
2022-02-17 17:58 ` Lukasz Luba
2022-02-17 18:18 ` Lukasz Luba
2022-02-22 17:05 ` Lukasz Luba
2022-02-22 18:12 ` Daniel Lezcano
2022-02-22 18:31 ` Lukasz Luba
2022-02-22 22:10 ` Daniel Lezcano
2022-02-23 9:10 ` Lukasz Luba
2022-02-07 7:30 ` [PATCH 2/2] powercap: DTPM: Check Energy Model type for power values scale Lukasz Luba
2022-02-07 10:41 ` [PATCH 0/2] Ignore Energy Model with abstract scale in IPA and DTPM Daniel Lezcano
2022-02-07 11:44 ` Lukasz Luba
2022-02-08 7:39 ` Daniel Lezcano
2022-02-08 9:47 ` Lukasz Luba
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