On 01/09/2013 12:20 PM, Namhyung Kim wrote:
> From: Namhyung Kim <namhyung....@lge.com>
>
> AFAICS @target cpu of select_idle_sibling() is always either prev_cpu
> or this_cpu. So no need to check it again and the conditionals can be
> consolidated.
>
> Cc: Mike Galbraith <efa...@gmx.de>
> Cc: Preeti U Murthy <pre...@linux.vnet.ibm.com>
> Cc: Vincent Guittot <vincent.guit...@linaro.org>
> Cc: Alex Shi <alex....@intel.com>
> Signed-off-by: Namhyung Kim <namhy...@kernel.org>
> ---
> kernel/sched/fair.c | 17 ++++-------------
> 1 file changed, 4 insertions(+), 13 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 5eea8707234a..af665814c216 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3254,25 +3254,16 @@ find_idlest_cpu(struct sched_group *group, struct
> task_struct *p, int this_cpu)
> */
> static int select_idle_sibling(struct task_struct *p, int target)
> {
> - int cpu = smp_processor_id();
> - int prev_cpu = task_cpu(p);
> struct sched_domain *sd;
> struct sched_group *sg;
> int i;
>
> /*
> - * If the task is going to be woken-up on this cpu and if it is
> - * already idle, then it is the right target.
> - */
> - if (target == cpu && idle_cpu(cpu))
> - return cpu;
> -
> - /*
> - * If the task is going to be woken-up on the cpu where it previously
> - * ran and if it is currently idle, then it the right target.
> + * If the task is going to be woken-up on this cpu or the cpu where it
> + * previously ran and it is already idle, then it is the right target.
> */
> - if (target == prev_cpu && idle_cpu(prev_cpu))
> - return prev_cpu;
> + if (idle_cpu(target))
> + return target;
>
> /*
> * Otherwise, iterate the domains and find an elegible idle cpu.
>
If NUMA_TTWU_BIAS or NUMA_TTWU_TO is true(it is false by
default),cpu/prev_cpu can be changed to be a random node_cpu(the node
that 'this_cpu' is on). In which case even if the node cpu is idle,it
would not be a viable target,looks like.Maybe that is why
select_idle_sibling() makes the check if the target is prev_cpu/this cpu.
Regards
Preeti U Murthy
--
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/
