linux-kernel - Re: [PATCH -next] sched/fair: Fix unused function warning

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Date:   Mon, 29 Mar 2021 14:35:29 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     YueHaibing <yuehaibing@...wei.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] sched/fair: Fix unused function warning

Hi,

On Sat, 27 Mar 2021 at 14:59, YueHaibing <yuehaibing@...wei.com> wrote:
>
> while CONFIG_NO_HZ_COMMON is not enabled, gcc warn this:
>
> kernel/sched/fair.c:8398:13: warning: ‘update_nohz_stats’ defined but not used [-Wunused-function]
>  static bool update_nohz_stats(struct rq *rq)
>              ^~~~~~~~~~~~~~~~~
>
> Move update_nohz_stats() to #ifdef block fix this.

Could you add a fix tag  ?
Fixes: 0826530de3cb ("sched/fair: Remove update of blocked load from
newidle_balance")

Also could you move update_nohz_stats() closer to its only caller
_nohz_idle_balance()

With these small nits above:

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

>
> Signed-off-by: YueHaibing <yuehaibing@...wei.com>
> ---
>  kernel/sched/fair.c | 40 ++++++++++++++++++----------------------
>  1 file changed, 18 insertions(+), 22 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 6d73bdbb2d40..c7a7ef97d167 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -8395,28 +8395,6 @@ group_type group_classify(unsigned int imbalance_pct,
>         return group_has_spare;
>  }
>
> -static bool update_nohz_stats(struct rq *rq)
> -{
> -#ifdef CONFIG_NO_HZ_COMMON
> -       unsigned int cpu = rq->cpu;
> -
> -       if (!rq->has_blocked_load)
> -               return false;
> -
> -       if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
> -               return false;
> -
> -       if (!time_after(jiffies, READ_ONCE(rq->last_blocked_load_update_tick)))
> -               return true;
> -
> -       update_blocked_averages(cpu);
> -
> -       return rq->has_blocked_load;
> -#else
> -       return false;
> -#endif
> -}
> -
>  /**
>   * update_sg_lb_stats - Update sched_group's statistics for load balancing.
>   * @env: The load balancing environment.
> @@ -10097,6 +10075,24 @@ static inline int on_null_domain(struct rq *rq)
>  }
>
>  #ifdef CONFIG_NO_HZ_COMMON
> +static bool update_nohz_stats(struct rq *rq)
> +{
> +       unsigned int cpu = rq->cpu;
> +
> +       if (!rq->has_blocked_load)
> +               return false;
> +
> +       if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
> +               return false;
> +
> +       if (!time_after(jiffies, READ_ONCE(rq->last_blocked_load_update_tick)))
> +               return true;
> +
> +       update_blocked_averages(cpu);
> +
> +       return rq->has_blocked_load;
> +}
> +
>  /*
>   * idle load balancing details
>   * - When one of the busy CPUs notice that there may be an idle rebalancing
> --
> 2.17.1
>