Hi Alex,
On 12/10/2012 01:52 PM, Alex Shi wrote:
> Except using runnable load average in background, move_tasks is also
> the key functions in load balance. We need consider the runnable load
> average in it in order to the apple to apple load comparison.
>
> Signed-off-by: Alex Shi <alex....@intel.com>
> ---
> kernel/sched/fair.c | 11 ++++++++++-
> 1 files changed, 10 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 6d893a6..bbb069c 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3741,6 +3741,15 @@ static unsigned long task_h_load(struct task_struct
> *p);
>
> static const unsigned int sched_nr_migrate_break = 32;
>
> +static unsigned long task_h_load_avg(struct task_struct *p)
> +{
> + u32 period = p->se.avg.runnable_avg_period;
> + if (!period)
> + return 0;
> +
> + return task_h_load(p) * p->se.avg.runnable_avg_sum / period;
^^^^^^^^^^^^
This might result in an overflow,considering you are multiplying two 32
bit integers.Below is how this is handled in
__update_task_entity_contrib in kernel/sched/fair.c
u32 contrib;
/* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */
contrib = se->avg.runnable_avg_sum * scale_load_down(se->load.weight);
contrib /= (se->avg.runnable_avg_period + 1);
se->avg.load_avg_contrib = scale_load(contrib);
Also why can't p->se.load_avg_contrib be used directly? as a return
value for task_h_load_avg? since this is already updated in
update_task_entity_contrib and update_group_entity_contrib.
> +}
> +
> /*
> * move_tasks tries to move up to imbalance weighted load from busiest to
> * this_rq, as part of a balancing operation within domain "sd".
> @@ -3776,7 +3785,7 @@ static int move_tasks(struct lb_env *env)
> if (throttled_lb_pair(task_group(p), env->src_cpu,
> env->dst_cpu))
> goto next;
>
> - load = task_h_load(p);
> + load = task_h_load_avg(p);
>
> if (sched_feat(LB_MIN) && load < 16 &&
> !env->sd->nr_balance_failed)
> goto next;
>
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/
