On 9 October 2014 14:16, Peter Zijlstra peterz@infradead.org wrote:
On Tue, Oct 07, 2014 at 02:13:36PM +0200, Vincent Guittot wrote:
+static inline bool +group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs) {
if ((sgs->group_capacity * 100) >(sgs->group_usage * env->sd->imbalance_pct))return true;Why the imb_pct there? We're looking for 100% utilization, not 130 or whatnot, right?
Having exactly 100% is quite difficult because of various rounding. So i have added a margin/threshold to prevent any excessive change of the state. I have just to use the same margin/threshold than in other place in load balance.
so the current threshold depends of the sched_level. it's around 14% at MC level
if (sgs->sum_nr_running < sgs->group_weight)return true;With the code as it stands, this is the cheaper test (no mults) so why is it second?
return false;+}
+static inline bool +group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs) +{
if (sgs->sum_nr_running <= sgs->group_weight)return false;if ((sgs->group_capacity * 100) <(sgs->group_usage * env->sd->imbalance_pct))return true;return false;}
Same thing here wrt imb_pct