[PATCH v2 11/11] sched: replace capacity by activity

[Vincent Guittot]

On 29 May 2014 16:02, Peter Zijlstra <peterz at infradead.org> wrote:
> On Fri, May 23, 2014 at 05:53:05PM +0200, Vincent Guittot wrote:
>> @@ -6052,8 +6006,8 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
>>                * with a large weight task outweighs the tasks on the system).
>>                */
>>               if (prefer_sibling && sds->local &&
>> -                 sds->local_stat.group_has_capacity)
>> -                     sgs->group_capacity = min(sgs->group_capacity, 1U);
>> +                 sds->local_stat.group_capacity > 0)
>> +                     sgs->group_capacity = min(sgs->group_capacity, 1L);
>>
>>               if (update_sd_pick_busiest(env, sds, sg, sgs)) {
>>                       sds->busiest = sg;
>> @@ -6228,7 +6182,7 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
>>                * have to drop below capacity to reach cpu-load equilibrium.
>>                */
>>               load_above_capacity =
>> -                     (busiest->sum_nr_running - busiest->group_capacity);
>> +                     (busiest->sum_nr_running - busiest->group_weight);
>>
>>               load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
>>               load_above_capacity /= busiest->group_power;
>
> I think you just broke PREFER_SIBLING here..

you mean by replacing the capacity which was reflecting the number of
core for SMT by the group_weight ?

>
> So we want PREFER_SIBLING to work on nr_running, not utilization because
> we want to spread single tasks around, regardless of their utilization.
>