linux-kernel - Re: [PATCH 3/4] sched/fair: Remove select_idle

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Date:   Wed, 27 Jan 2021 11:39:41 +0100
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Li Aubrey <aubrey.li@...ux.intel.com>,
        Qais Yousef <qais.yousef@....com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] sched/fair: Remove select_idle_smt()

On Mon, 25 Jan 2021 at 09:59, Mel Gorman <mgorman@...hsingularity.net> wrote:
>
> From: Peter Zijlstra <peterz@...radead.org>
>
> From: Peter Zijlstra (Intel) <peterz@...radead.org>
>
> In order to make the next patch more readable, and to quantify the
> actual effectiveness of this pass, start by removing it.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>

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

> ---
>  kernel/sched/fair.c | 30 ------------------------------
>  1 file changed, 30 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index c8d8e185cf3b..fe587350ea14 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6101,27 +6101,6 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int
>         return -1;
>  }
>
> -/*
> - * Scan the local SMT mask for idle CPUs.
> - */
> -static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
> -{
> -       int cpu;
> -
> -       if (!static_branch_likely(&sched_smt_present))
> -               return -1;
> -
> -       for_each_cpu(cpu, cpu_smt_mask(target)) {
> -               if (!cpumask_test_cpu(cpu, p->cpus_ptr) ||
> -                   !cpumask_test_cpu(cpu, sched_domain_span(sd)))
> -                       continue;
> -               if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
> -                       return cpu;
> -       }
> -
> -       return -1;
> -}
> -
>  #else /* CONFIG_SCHED_SMT */
>
>  static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
> @@ -6129,11 +6108,6 @@ static inline int select_idle_core(struct task_struct *p, struct sched_domain *s
>         return -1;
>  }
>
> -static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
> -{
> -       return -1;
> -}
> -
>  #endif /* CONFIG_SCHED_SMT */
>
>  /*
> @@ -6323,10 +6297,6 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
>         if ((unsigned)i < nr_cpumask_bits)
>                 return i;
>
> -       i = select_idle_smt(p, sd, target);
> -       if ((unsigned)i < nr_cpumask_bits)
> -               return i;
> -
>         return target;
>  }
>
> --
> 2.26.2
>