Re: [PATCH v7 6/7] sched: replace capacity_factor by usage

On Tue, Oct 07, 2014 at 02:13:36PM +0200, Vincent Guittot wrote:

@@ -6214,17 +6178,21 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd /* * In case the child domain prefers tasks go to siblings

•  * first, lower the sg capacity to one so that we'll try
  

  • and move all the excess tasks away. We lower the capacity
  • of a group only if the local group has the capacity to fit

•  * these excess tasks, i.e. group_capacity > 0. The
  

  • extra check prevents the case where you always pull from the
  • heaviest group when it is already under-utilized (possible
  • with a large weight task outweighs the tasks on the system).
  */ if (prefer_sibling && sds->local &&

•     group_has_capacity(env, &sds->local_stat)) {
  

• 	if (sgs->sum_nr_running > 1)
  

• 		sgs->group_no_capacity = 1;
  

• 	sgs->group_capacity = min(sgs->group_capacity,
  

• 				SCHED_CAPACITY_SCALE);
  

• }
  

if (update_sd_pick_busiest(env, sds, sg, sgs)) { sds->busiest = sg;

@@ -6490,8 +6460,8 @@ static struct sched_group *find_busiest_group(struct lb_env *env) goto force_balance; /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */

• if (env->idle == CPU_NEWLY_IDLE && local->group_has_free_capacity &&

•    !busiest->group_has_free_capacity)
  

• if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&

•    busiest->group_no_capacity)
  

  goto force_balance;

/*

This is two calls to group_has_capacity() on the local group. Why not compute once in update_sd_lb_stats()?