On Tue, Aug 26, 2014 at 01:06:51PM +0200, Vincent Guittot wrote:
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 18db43e..60ae1ce 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6049,6 +6049,14 @@ static bool update_sd_pick_busiest(struct lb_env *env,
> return true;
> }
>
> + /*
> + * The group capacity is reduced probably because of activity from other
> + * sched class or interrupts which use part of the available capacity
> + */
> + if ((sg->sgc->capacity_orig * 100) > (sgs->group_capacity *
> + env->sd->imbalance_pct))
> + return true;
> +
> return false;
> }
>
> @@ -6534,13 +6542,23 @@ static int need_active_balance(struct lb_env *env)
> struct sched_domain *sd = env->sd;
>
> if (env->idle == CPU_NEWLY_IDLE) {
> + int src_cpu = env->src_cpu;
>
> /*
> * ASYM_PACKING needs to force migrate tasks from busy but
> * higher numbered CPUs in order to pack all tasks in the
> * lowest numbered CPUs.
> */
> - if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu >
> env->dst_cpu)
> + if ((sd->flags & SD_ASYM_PACKING) && src_cpu > env->dst_cpu)
> + return 1;
> +
> + /*
> + * If the CPUs share their cache and the src_cpu's capacity is
> + * reduced because of other sched_class or IRQs, we trig an
> + * active balance to move the task
> + */
> + if ((capacity_orig_of(src_cpu) * 100) > (capacity_of(src_cpu) *
> + sd->imbalance_pct))
> return 1;
> }
Should you not also check -- in both cases -- that the destination is
any better?
Also, there's some obvious repetition going on there, maybe add a
helper?
Also, both sites should probably ensure they're operating in the
non-saturated/overloaded scenario. Because as soon as we're completely
saturated we want SMP nice etc. and that all already works right
(presumably).
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