Re: [PATCH] sched/fair: Simplify the code of should_we_balance()

Vincent Guittot
2020-04-14T07:25:24Z

On Sat, 11 Apr 2020 at 11:21, Peng Wang <rocking@linux.alibaba.com> wrote:
>
> We only consider group_balance_cpu() after there is no idle
> cpu. So, just do comparison before return at these two cases.
>
> Signed-off-by: Peng Wang <rocking@linux.alibaba.com>

With the small fix in the comment below
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>

> ---
> kernel/sched/fair.c | 16 +++++-----------
> 1 file changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 1ea3ddd..81b2c647 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -9413,7 +9413,7 @@ static int active_load_balance_cpu_stop(void *data);
> static int should_we_balance(struct lb_env *env)
> {
> struct sched_group *sg = env->sd->groups;
> - int cpu, balance_cpu = -1;
> + int cpu;
>
> /*
> * Ensure the balancing environment is consistent; can happen
> @@ -9434,18 +9434,12 @@ static int should_we_balance(struct lb_env *env)
> if (!idle_cpu(cpu))
> continue;
>
> - balance_cpu = cpu;
> - break;
> + /* Are we the first idle CPU? */
> + return cpu == env->dst_cpu;
> }
>
> - if (balance_cpu == -1)
> - balance_cpu = group_balance_cpu(sg);
> -
> - /*
> - * First idle CPU or the first CPU(busiest) in this sched group
> - * is eligible for doing load balancing at this and above domains.
> - */
> - return balance_cpu == env->dst_cpu;
> + /* Are we the first balance CPU of this group? */

/* Are we the first CPU of this group ? */

> + return group_balance_cpu(sg) == env->dst_cpu;
> }
>
> /*
> --
> 2.9.5
>