Re: [PATCH v2 3/6] sched: don't consider other cpus in our group incase of NEWLY_IDLE

From: Peter Zijlstra
Date: Mon Apr 22 2013 - 07:59:57 EST


On Tue, 2013-03-26 at 15:01 +0900, Joonsoo Kim wrote:
> Commit 88b8dac0 makes load_balance() consider other cpus in its group,
> regardless of idle type. When we do NEWLY_IDLE balancing, we should not
> consider it, because a motivation of NEWLY_IDLE balancing is to turn
> this cpu to non idle state if needed. This is not the case of other cpus.
> So, change code not to consider other cpus for NEWLY_IDLE balancing.
>
> With this patch, assign 'if (pulled_task) this_rq->idle_stamp = 0'
> in idle_balance() is corrected, because NEWLY_IDLE balancing doesn't
> consider other cpus. Assigning to 'this_rq->idle_stamp' is now valid.
>
> Cc: Srivatsa Vaddagiri <vatsa@xxxxxxxxxxxxxxxxxx>
> Acked-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 9d693d0..3f8c4f2 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5007,8 +5007,17 @@ static int load_balance(int this_cpu, struct rq *this_rq,
> .cpus = cpus,
> };
>
> + /* For NEWLY_IDLE load_balancing, we don't need to consider
> + * other cpus in our group */
> + if (idle == CPU_NEWLY_IDLE) {
> + env.dst_grpmask = NULL;
> + /* we don't care max_lb_iterations in this case,
> + * in following patch, this will be removed */

This comment violates coding style; comments looks like:

/* this is a single-line comment */

or

/*
* this is a multi-
* line comment.
*/

Luckily you're deleting these offensive lines again in patch 6 :-)

> + max_lb_iterations = 0;
> + } else {
> + max_lb_iterations = cpumask_weight(env.dst_grpmask);
> + }
> cpumask_copy(cpus, cpu_active_mask);
> - max_lb_iterations = cpumask_weight(env.dst_grpmask);
>
> schedstat_inc(sd, lb_count[idle]);
>


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