On 9 October 2014 16:16, Peter Zijlstra <pet...@infradead.org> wrote: > 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()?
mainly because of the place in the code, so it is not always used during load balance unlike group_no_capacity Now that i have said that, i just noticed that it's better to move the call to the last tested condition + if (env->idle == CPU_NEWLY_IDLE && busiest->group_no_capacity && + group_has_capacity(env, local)) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/