linux-kernel - Re: [RFC,v2 3/3] sched: ignore task_h_load for CPU_NEWLY

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Date:   Wed, 08 Feb 2017 10:19:48 +0100
From:   Mike Galbraith <efault@....de>
To:     Uladzislau Rezki <urezki@...il.com>, Ingo Molnar <mingo@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Uladzislau 2 Rezki <uladzislau2.rezki@...ymobile.com>
Subject: Re: [RFC,v2 3/3] sched: ignore task_h_load for CPU_NEWLY_IDLE

On Wed, 2017-02-08 at 09:43 +0100, Uladzislau Rezki wrote:
> From: Uladzislau 2 Rezki <uladzislau2.rezki@...ymobile.com>
> 
> A load balancer calculates imbalance factor for particular shed
                                                             ^sched
> domain and tries to steal up the prescribed amount of weighted load.
> However, a small imbalance factor would sometimes prevent us from
> stealing any tasks at all. When a CPU is newly idle, it should
> steal first task which passes a migration criteria.
                         s/passes a/meets the
> 
> Signed-off-by: Uladzislau 2 Rezki <uladzislau2.rezki@...ymobile.com>
> ---
>  kernel/sched/fair.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 232ef3c..29e0d7f 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> 	> 	> env->loop++;
> @@ -6824,8 +6832,9 @@ static int detach_tasks(struct lb_env *env)
>  > 	> 	> if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
>  > 	> 	> 	> goto next;
>  
> -> 	> 	> if ((load / 2) > env->imbalance)
> -> 	> 	> 	> goto next;
> +> 	> 	> if (env->idle != CPU_NEWLY_IDLE)
> +> 	> 	> 	> if ((load / 2) > env->imbalance)
> +> 	> 	> 	> 	> goto next;

Those two ifs could be one ala if (foo && bar).