On Tue, Aug 26, 2014 at 01:06:54PM +0200, Vincent Guittot wrote:
+static inline int group_has_free_capacity(struct sg_lb_stats *sgs,
struct lb_env *env){
- if ((sgs->group_capacity_orig * 100) >
(sgs->group_utilization * env->sd->imbalance_pct))return 1;- if (sgs->sum_nr_running < sgs->group_weight)
return 1;
- return 0;
+} +static inline int group_is_overloaded(struct sg_lb_stats *sgs,
struct lb_env *env)+{
- if (sgs->sum_nr_running <= sgs->group_weight)
return 0;
- if ((sgs->group_capacity_orig * 100) <
(sgs->group_utilization * env->sd->imbalance_pct))return 1;
- return 0;
}
I'm confused about the utilization vs capacity_orig. I see how we should maybe scale things with the capacity when comparing between CPUs/groups, but not on the same CPU/group.
I would have expected something simple like:
static inline bool group_has_capacity() { /* Is there a spare cycle? */ if (sgs->group_utilization < sgs->group_weight * SCHED_LOAD_SCALE) return true;
/* Are there less tasks than logical CPUs? */ if (sgs->sum_nr_running < sgs->group_weight) return true;
return false; }
Where group_utilization a pure sum of running_avg.
Now this has a hole when there are RT tasks on the system, in that case the utilization will never hit 1, but we could fix that another way. I don't think the capacity_orig thing is right.