linux-kernel - Re: [PATCH] thermal: gov_power_allocator: Fix incorrect calculation in divvy_up

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Message-ID: <9cc02f9e-9326-4fe1-820b-ca725f68de29@arm.com>
Date: Fri, 21 Feb 2025 10:35:30 +0000
From: Lukasz Luba <lukasz.luba@....com>
To: "Rafael J. Wysocki" <rafael@...nel.org>, Yu-Che Cheng <giver@...omium.org>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>,
 Zhang Rui <rui.zhang@...el.com>,
 "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org, Chen-Yu Tsai <wenst@...omium.org>
Subject: Re: [PATCH] thermal: gov_power_allocator: Fix incorrect calculation
 in divvy_up_power



On 2/20/25 19:45, Rafael J. Wysocki wrote:
> On Wed, Feb 19, 2025 at 8:07 AM Yu-Che Cheng <giver@...omium.org> wrote:
>>
>> divvy_up_power should use weighted_req_power instead of req_power to
>> calculate the granted_power. Otherwise, the granted_power may be
>> unexpected as the denominator total_req_power is weighted sum.
> 
> Yes, this is what's happening, to my eyes.
> 
>> This is a mistake during the previous refactor.
>>
>> Replace the req_power with weighted_req_power in divvy_up_power
>> calculation.
>>
>> Fixes: 912e97c67cc3 ("thermal: gov_power_allocator: Move memory allocation out of throttle()")
>> Signed-off-by: Yu-Che Cheng <giver@...omium.org>
>> ---
>>   drivers/thermal/gov_power_allocator.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c
>> index 3b644de3292e..3b626db55b2b 100644
>> --- a/drivers/thermal/gov_power_allocator.c
>> +++ b/drivers/thermal/gov_power_allocator.c
>> @@ -370,7 +370,7 @@ static void divvy_up_power(struct power_actor *power, int num_actors,
>>
>>          for (i = 0; i < num_actors; i++) {
>>                  struct power_actor *pa = &power[i];
>> -               u64 req_range = (u64)pa->req_power * power_range;
>> +               u64 req_range = (u64)pa->weighted_req_power * power_range;
>>
>>                  pa->granted_power = DIV_ROUND_CLOSEST_ULL(req_range,
>>                                                            total_req_power);
>>
>> ---
> 
> And the fix looks good to me.
> 
> Lukasz, any concerns?

Good catch! It went through since the test didn't set different weights.

Thanks for the fix!

Reviewed-by: Lukasz Luba <lukasz.luba@....com>