Messages in this thread |  | | From | Vincent Guittot <> | Date | Thu, 9 Oct 2014 16:28:58 +0200 | Subject | Re: [PATCH v7 6/7] sched: replace capacity_factor by usage |
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On 9 October 2014 16:16, Peter Zijlstra <peterz@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))
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