linux-kernel - Re: [PATCH] sched/fair: move capacity

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Date:   Tue, 11 Dec 2018 08:46:19 +0100
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>, smuchun@...il.com,
        Morten Rasmussen <morten.rasmussen@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched/fair: move capacity_margin definition into #ifdef

Hi Arnd,

On Mon, 10 Dec 2018 at 22:01, Arnd Bergmann <arnd@...db.de> wrote:
>
> Marking the variable static showed that it's only used for
> SMP builds, as seen from this warning:
>
> kernel/sched/fair.c:119:21: error: 'capacity_margin' defined but not used [-Werror=unused-variable]
>  static unsigned int capacity_margin   = 1280;

Olof sent a similar patch 2 weeks ago: https://lkml.org/lkml/2018/11/26/115

Vincent
>
> This has apparently been true since the variable has first been
> introduced, but only now started causing a compile time warning.
>
> Fixes: ed8885a14433 ("sched/fair: Make some variables static")
> Fixes: 3273163c6775 ("sched/fair: Let asymmetric CPU configurations balance at wake-up")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  kernel/sched/fair.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index e30dea59d215..27928809e6ed 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -110,14 +110,6 @@ int __weak arch_asym_cpu_priority(int cpu)
>  unsigned int sysctl_sched_cfs_bandwidth_slice          = 5000UL;
>  #endif
>
> -/*
> - * The margin used when comparing utilization with CPU capacity:
> - * util * margin < capacity * 1024
> - *
> - * (default: ~20%)
> - */
> -static unsigned int capacity_margin                    = 1280;
> -
>  static inline void update_load_add(struct load_weight *lw, unsigned long inc)
>  {
>         lw->weight += inc;
> @@ -3046,6 +3038,14 @@ static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
>  }
>
>  #ifdef CONFIG_SMP
> +/*
> + * The margin used when comparing utilization with CPU capacity:
> + * util * margin < capacity * 1024
> + *
> + * (default: ~20%)
> + */
> +static unsigned int capacity_margin                    = 1280;
> +
>  #ifdef CONFIG_FAIR_GROUP_SCHED
>  /**
>   * update_tg_load_avg - update the tg's load avg
> --
> 2.20.0
>