Re: [PATCH] Prevent immediate process rescheduling

[Ingo Molnar <mingo@elte.hu>]

(fixed the Cc: lines)

* Mark Langsdorf <mark.langsdorf@amd.com> wrote:

> Prevent the scheduler from immediately rescheduling a process
> that just yielded if there is another process available.
> 
> Originally suggested by Mike Galbraith (efault@gmx.de).
> 
> Signed-off-by: Mark Langsdorf <mark.langsdorf@amd.com>
> ---
>  kernel/sched_fair.c |   16 +++++++++++++++-
>  1 files changed, 15 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
> index 652e8bd..4fad08f 100644
> --- a/kernel/sched_fair.c
> +++ b/kernel/sched_fair.c
> @@ -353,11 +353,25 @@ static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
>  static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
>  {
>  	struct rb_node *left = cfs_rq->rb_leftmost;
> +	struct sched_entity *se, *curr;
>  
>  	if (!left)
>  		return NULL;
>  
> -	return rb_entry(left, struct sched_entity, run_node);
> +	se = rb_entry(left, struct sched_entity, run_node);
> +	curr = &current->se;
> +
> +	/* 
> +	 * Don't select the entity who just tried to schedule away
> +	 * if there's another entity available.
> +	 */
> +	if (unlikely(se == curr && cfs_rq->nr_running > 1)) {
> +		struct rb_node *next_node = rb_next(&curr->run_node);
> +		if (next_node)
> +			se = rb_entry(next_node, struct sched_entity, run_node);
> +	}
> +
> +	return se;
>  }

I suspect some real workload is the motivation of this - what is that 
workload?

	Ingo