On Mon, 2013-02-18 at 18:31 +0530, Srikar Dronamraju wrote:
> pick_next_entity() prefers next, then last. However code checks if the
> left entity can be skipped even if next / last is set.
>
> Check if left entity should be skipped only if next/last is not set.
You fail to explain why its a problem and continue to make a horrid mess
of the code..
> Signed-off-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com>
> ---
> kernel/sched/fair.c | 31 +++++++++++++++----------------
> 1 files changed, 15 insertions(+), 16 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index fdee793..cc97b12 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -1900,27 +1900,26 @@ static struct sched_entity *pick_next_entity(struct
> cfs_rq *cfs_rq)
> struct sched_entity *left = se;
>
> /*
> - * Avoid running the skip buddy, if running something else can
> - * be done without getting too unfair.
> + * Someone really wants next to run. If it's not unfair, run it.
> */
> - if (cfs_rq->skip == se) {
> - struct sched_entity *second = __pick_next_entity(se);
> + if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) {
> + se = cfs_rq->next;
> + } else if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) <
> 1) {
> + /*
> + * Prefer last buddy, try to return the CPU to a preempted
> + * task.
> + */
> + se = cfs_rq->last;
> + } else if (cfs_rq->skip == left) {
> + /*
> + * Avoid running the skip buddy, if running something else
> + * can be done without getting too unfair.
> + */
> + struct sched_entity *second = __pick_next_entity(left);
> if (second && wakeup_preempt_entity(second, left) < 1)
> se = second;
> }
>
> - /*
> - * Prefer last buddy, try to return the CPU to a preempted task.
> - */
> - if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
> - se = cfs_rq->last;
> -
> - /*
> - * Someone really wants this to run. If it's not unfair, run it.
> - */
> - if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
> - se = cfs_rq->next;
> -
> clear_buddies(cfs_rq, se);
>
> return se;
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
