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Message-ID: <2a97cf28-7e47-04c7-edcb-41adbd20ccd9@arm.com>
Date:   Tue, 6 Dec 2022 10:29:58 +0000
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Subject: Re: [PATCH] cpufreq: schedutil: Optimize operations with single max
 CPU capacity
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To:     Viresh Kumar <viresh.kumar@linaro.org>
Cc:     linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        rafael@kernel.org, dietmar.eggemann@arm.com,
        vincent.guittot@linaro.org, saravanak@google.com,
        wusamuel@google.com, isaacmanjarres@google.com,
        kernel-team@android.com, juri.lelli@redhat.com,
        peterz@infradead.org, mingo@redhat.com, rostedt@goodmis.org,
        bsegall@google.com, mgorman@suse.de
References: <20221206101021.18113-1-lukasz.luba@arm.com>
 <20221206101629.dbcuv3zdso44w3cq@vireshk-i7>
From:   Lukasz Luba <lukasz.luba@arm.com>
In-Reply-To: <20221206101629.dbcuv3zdso44w3cq@vireshk-i7>
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On 12/6/22 10:16, Viresh Kumar wrote:
> On 06-12-22, 10:10, Lukasz Luba wrote:
>> The max CPU capacity is the same for all CPUs sharing frequency domain
>> and thus 'policy' object. There is a way to avoid heavy operations
>> in a loop for each CPU by leveraging this knowledge. Thus, simplify
>> the looping code in the sugov_next_freq_shared() and drop heavy
>> multiplications. Instead, use simple max() to get the highest utilization
>> from these CPUs. This is useful for platforms with many (4 or 6) little
>> CPUs.
>>
>> The max CPU capacity must be fetched every time we are called, due to
>> difficulties during the policy setup, where we are not able to get the
>> normalized CPU capacity at the right time.
>>
>> The stored value in sugov_policy::max is also than used in
>> sugov_iowait_apply() to calculate the right boost. Thus, that field is
>> useful to have in that sugov_policy struct.
>>
>> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
> 
> Can you please divide this into two patches, one for just moving max
> and one for looping optimization ? Else we may end up reverting
> everything once again.
> 

OK, I can do that. Thanks for having a look!