From: Thara Gopinath <thara.gopinath@linaro.org>
To: Lukasz Luba <lukasz.luba@arm.com>,
linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org,
linux-arm-msm@vger.kernel.org, steev@kali.org,
sudeep.holla@arm.com, will@kernel.org, catalin.marinas@arm.com,
linux@armlinux.org.uk, gregkh@linuxfoundation.org,
rafael@kernel.org, viresh.kumar@linaro.org, amitk@kernel.org,
daniel.lezcano@linaro.org, amit.kachhap@gmail.com,
bjorn.andersson@linaro.org, agross@kernel.org
Subject: Re: [PATCH v4 4/5] cpufreq: qcom-cpufreq-hw: Use new thermal pressure update function
Date: Mon, 15 Nov 2021 18:39:18 -0500 [thread overview]
Message-ID: <911760d9-b137-5c79-d072-c2f473a3cc6a@linaro.org> (raw)
In-Reply-To: <02a848c8-a672-f3df-7144-979a9df71fcb@linaro.org>
On 11/15/21 3:57 PM, Thara Gopinath wrote:
>
>
> On 11/9/21 2:57 PM, Lukasz Luba wrote:
>> Thermal pressure provides a new API, which allows to use CPU frequency
>> as an argument. That removes the need of local conversion to capacity.
>> Use this new API and remove old local conversion code.
>>
>> The new arch_update_thermal_pressure() also accepts boost frequencies,
>> which solves issue in the driver code with wrong reduced capacity
>> calculation. The reduced capacity was calculated wrongly due to
>> 'policy->cpuinfo.max_freq' used as a divider. The value present there was
>> actually the boost frequency. Thus, even a normal maximum frequency value
>> which corresponds to max CPU capacity (arch_scale_cpu_capacity(cpu_id))
>> is not able to remove the capping.
Also I failed to mention that, currently freq_factor is initialized as
cpuinfo.max_freq / 1000 which means again all the issues you mentioned
below can be hit, if some cpufreq driver decides to set boost at init.
I have sent a patch earlier today to fix this.
https://lore.kernel.org/linux-arm-msm/20211115201010.68567-1-thara.gopinath@linaro.org/T/#u
--
Warm Regards
Thara (She/Her/Hers)
>
> Yes, although cpuinfo.max_freq does not reflect the boost frequency
> unless boost is enabled atleast once. I have sent a patch to fix this.
> But I agree that using cpuinfo.max_freq has issues you have mentioned in
> this patch if boost is enabled once.
>
> So, for this patch
>
> Reviewed-by: Thara Gopinath <thara.gopinath@linaro.org>
>
> Warm Regards
> Thara (She/Her/Hers)
>>
>> The second side effect which is solved is that the reduced frequency
>> wasn't
>> properly translated into the right reduced capacity,
>> e.g.
>> boost frequency = 3000MHz (stored in policy->cpuinfo.max_freq)
>> max normal frequency = 2500MHz (which is 1024 capacity)
>> 2nd highest frequency = 2000MHz (which translates to 819 capacity)
>>
>> Then in a scenario when the 'throttled_freq' max allowed frequency was
>> 2000MHz the driver translated it into 682 capacity:
>> capacity = 1024 * 2000 / 3000 = 682
>> Then set the pressure value bigger than actually applied by the HW:
>> max_capacity - capacity => 1024 - 682 = 342 (<- thermal pressure)
>> Which was causing higher throttling and misleading task scheduler
>> about available CPU capacity.
>> A proper calculation in such case should be:
>> capacity = 1024 * 2000 / 2500 = 819
>> 1024 - 819 = 205 (<- thermal pressure)
>>
>> This patch relies on the new arch_update_thermal_pressure() handling
>> correctly such use case (with boost frequencies).
>>
>> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
>> ---
>> drivers/cpufreq/qcom-cpufreq-hw.c | 15 +++------------
>> 1 file changed, 3 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c
>> b/drivers/cpufreq/qcom-cpufreq-hw.c
>> index 0138b2ec406d..248135e5087e 100644
>> --- a/drivers/cpufreq/qcom-cpufreq-hw.c
>> +++ b/drivers/cpufreq/qcom-cpufreq-hw.c
>> @@ -275,10 +275,10 @@ static unsigned int
>> qcom_lmh_get_throttle_freq(struct qcom_cpufreq_data *data)
>> static void qcom_lmh_dcvs_notify(struct qcom_cpufreq_data *data)
>> {
>> - unsigned long max_capacity, capacity, freq_hz, throttled_freq;
>> struct cpufreq_policy *policy = data->policy;
>> int cpu = cpumask_first(policy->cpus);
>> struct device *dev = get_cpu_device(cpu);
>> + unsigned long freq_hz, throttled_freq;
>> struct dev_pm_opp *opp;
>> unsigned int freq;
>> @@ -295,17 +295,8 @@ static void qcom_lmh_dcvs_notify(struct
>> qcom_cpufreq_data *data)
>> throttled_freq = freq_hz / HZ_PER_KHZ;
>> - /* Update thermal pressure */
>> -
>> - max_capacity = arch_scale_cpu_capacity(cpu);
>> - capacity = mult_frac(max_capacity, throttled_freq,
>> policy->cpuinfo.max_freq);
>> -
>> - /* Don't pass boost capacity to scheduler */
>> - if (capacity > max_capacity)
>> - capacity = max_capacity;
>> -
>> - arch_set_thermal_pressure(policy->related_cpus,
>> - max_capacity - capacity);
>> + /* Update thermal pressure (the boost frequencies are accepted) */
>> + arch_update_thermal_pressure(policy->related_cpus, throttled_freq);
>> /*
>> * In the unlikely case policy is unregistered do not enable
>>
>
next prev parent reply other threads:[~2021-11-16 3:09 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-09 19:57 [PATCH v4 0/5] Refactor thermal pressure update to avoid code duplication Lukasz Luba
2021-11-09 19:57 ` [PATCH v4 1/5] arch_topology: Introduce thermal pressure update function Lukasz Luba
2021-11-16 23:39 ` Thara Gopinath
2021-11-23 9:09 ` Lukasz Luba
2021-11-09 19:57 ` [PATCH v4 2/5] thermal: cpufreq_cooling: Use new " Lukasz Luba
2021-11-09 19:57 ` [PATCH v4 3/5] cpufreq: qcom-cpufreq-hw: Update offline CPUs per-cpu thermal pressure Lukasz Luba
2021-11-09 19:57 ` [PATCH v4 4/5] cpufreq: qcom-cpufreq-hw: Use new thermal pressure update function Lukasz Luba
2021-11-15 20:57 ` Thara Gopinath
2021-11-15 23:39 ` Thara Gopinath [this message]
2021-11-16 8:28 ` Lukasz Luba
2021-11-16 8:30 ` Lukasz Luba
2021-11-09 19:57 ` [PATCH v4 5/5] arch_topology: Remove unused topology_set_thermal_pressure() and related Lukasz Luba
2021-11-11 3:15 ` [PATCH v4 0/5] Refactor thermal pressure update to avoid code duplication Viresh Kumar
2021-11-23 9:11 ` Lukasz Luba
2021-11-23 9:45 ` Viresh Kumar
2021-11-23 9:46 ` Lukasz Luba
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