linux-kernel - Re: [PATCH v2 1/4] sched/uclamp: Make uclamp_util

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Date:   Tue, 10 Dec 2019 18:31:22 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     Dietmar Eggemann <dietmar.eggemann@....com>,
        linux-kernel@...r.kernel.org
Cc:     peterz@...radead.org, mingo@...nel.org, vincent.guittot@...aro.org,
        patrick.bellasi@...bug.net, qperret@...gle.com,
        qais.yousef@....com, morten.rasmussen@....com
Subject: Re: [PATCH v2 1/4] sched/uclamp: Make uclamp_util_*() helpers use and
 return UL values

On 10/12/2019 18:09, Dietmar Eggemann wrote:
> On 03/12/2019 16:59, Valentin Schneider wrote:
> 
> [...]
> 
>> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
>> index 280a3c735935..f1d035e5df7e 100644
>> --- a/kernel/sched/sched.h
>> +++ b/kernel/sched/sched.h
>> @@ -2303,15 +2303,15 @@ static inline void cpufreq_update_util(struct rq *rq, unsigned int flags) {}
>>  unsigned int uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id);
>>  
>>  static __always_inline
>> -unsigned int uclamp_util_with(struct rq *rq, unsigned int util,
>> -			      struct task_struct *p)
>> +unsigned long uclamp_util_with(struct rq *rq, unsigned long util,
>> +			       struct task_struct *p)
>>  {
>> -	unsigned int min_util = READ_ONCE(rq->uclamp[UCLAMP_MIN].value);
>> -	unsigned int max_util = READ_ONCE(rq->uclamp[UCLAMP_MAX].value);
>> +	unsigned long min_util = READ_ONCE(rq->uclamp[UCLAMP_MIN].value);
>> +	unsigned long max_util = READ_ONCE(rq->uclamp[UCLAMP_MAX].value);
>>  
>>  	if (p) {
>> -		min_util = max(min_util, uclamp_eff_value(p, UCLAMP_MIN));
>> -		max_util = max(max_util, uclamp_eff_value(p, UCLAMP_MAX));
>> +		min_util = max_t(unsigned long, min_util, uclamp_eff_value(p, UCLAMP_MIN));
>> +		max_util = max_t(unsigned long, max_util, uclamp_eff_value(p, UCLAMP_MAX));
>>  	}
>>  
>>  	/*
>> @@ -2325,17 +2325,17 @@ unsigned int uclamp_util_with(struct rq *rq, unsigned int util,
>>  	return clamp(util, min_util, max_util);
>>  }
>>  
>> -static inline unsigned int uclamp_util(struct rq *rq, unsigned int util)
>> +static inline unsigned long uclamp_util(struct rq *rq, unsigned long util)
>>  {
>>  	return uclamp_util_with(rq, util, NULL);
>>  }
>>  #else /* CONFIG_UCLAMP_TASK */
>> -static inline unsigned int uclamp_util_with(struct rq *rq, unsigned int util,
>> -					    struct task_struct *p)
>> +static inline unsigned long uclamp_util_with(struct rq *rq, unsigned long util,
>> +					     struct task_struct *p)
>>  {
>>  	return util;
>>  }
>> -static inline unsigned int uclamp_util(struct rq *rq, unsigned int util)
>> +static inline unsigned long uclamp_util(struct rq *rq, unsigned long util)
>>  {
>>  	return util;
>>  }
> 
> There doesn't seem to be any user of uclamp_util(), only uclamp_util_with()?
> 

It was added in

  982d9cdc22c9 ("sched/cpufreq, sched/uclamp: Add clamps for FAIR and RT tasks")

uclamp_util_with() followed closely in

  9d20ad7dfc9a ("sched/uclamp: Add uclamp_util_with()")

and the sole uclamp_util() user (schedutil_cpu_util()) moved to the latter
in 

  af24bde8df20 ("sched/uclamp: Add uclamp support to energy_compute()")


So it does seem like we could get rid of it - I could see it being useful
later on, but it's useless right now.