linux-kernel - Re: [PATCH v2 1/4] sched/fair: always used unsigned long for utilization

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Date:   Wed, 6 Dec 2017 09:56:34 +0100
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Patrick Bellasi <patrick.bellasi@....com>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Paul Turner <pjt@...gle.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Todd Kjos <tkjos@...roid.com>,
        Joel Fernandes <joelaf@...gle.com>
Subject: Re: [PATCH v2 1/4] sched/fair: always used unsigned long for utilization

On 5 December 2017 at 18:10, Patrick Bellasi <patrick.bellasi@....com> wrote:
> Utilization and capacity are tracked as unsigned long, however some
> functions using them return an int which is ultimately assigned back to
> unsigned long variables.
>
> Since there is not scope on using a different and signed type, this
> consolidate the signature of functions returning utilization to always
> use the native type.
> As well as improving code consistency this is expected also benefits
> code paths where utilizations should be clamped by avoiding further type
> conversions or ugly type casts.
>
> Signed-off-by: Patrick Bellasi <patrick.bellasi@....com>
> Reviewed-by: Chris Redpath <chris.redpath@....com>
> Reviewed-by: Brendan Jackman <brendan.jackman@....com>
> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@....com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Vincent Guittot <vincent.guittot@...aro.org>
> Cc: Morten Rasmussen <morten.rasmussen@....com>
> Cc: Dietmar Eggemann <dietmar.eggemann@....com>
> Cc: linux-kernel@...r.kernel.org

Acked-by: Vincent Guittot <vincent.guittot@...aro.org>

>
> ---
> Changes v1->v2:
>  - rebase on top of v4.15-rc2
>  - tested that overhauled PELT code does not affect the util_est
> ---
>  kernel/sched/fair.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 4037e19bbca2..ad21550d008c 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5721,8 +5721,8 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p,
>         return affine;
>  }
>
> -static inline int task_util(struct task_struct *p);
> -static int cpu_util_wake(int cpu, struct task_struct *p);
> +static inline unsigned long task_util(struct task_struct *p);
> +static unsigned long cpu_util_wake(int cpu, struct task_struct *p);
>
>  static unsigned long capacity_spare_wake(int cpu, struct task_struct *p)
>  {
> @@ -6203,7 +6203,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
>   * capacity_orig) as it useful for predicting the capacity required after task
>   * migrations (scheduler-driven DVFS).
>   */
> -static int cpu_util(int cpu)
> +static unsigned long cpu_util(int cpu)
>  {
>         unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
>         unsigned long capacity = capacity_orig_of(cpu);
> @@ -6211,7 +6211,7 @@ static int cpu_util(int cpu)
>         return (util >= capacity) ? capacity : util;
>  }
>
> -static inline int task_util(struct task_struct *p)
> +static inline unsigned long task_util(struct task_struct *p)
>  {
>         return p->se.avg.util_avg;
>  }
> @@ -6220,7 +6220,7 @@ static inline int task_util(struct task_struct *p)
>   * cpu_util_wake: Compute cpu utilization with any contributions from
>   * the waking task p removed.
>   */
> -static int cpu_util_wake(int cpu, struct task_struct *p)
> +static unsigned long cpu_util_wake(int cpu, struct task_struct *p)
>  {
>         unsigned long util, capacity;
>
> --
> 2.14.1
>