On Thu, Jan 15, 2015 at 11:09:28AM +0100, Vincent Guittot wrote:
Finally, the sched_group->sched_group_capacity->capacity_orig has been removed because it's no more used during load balance.
Maybe do that in a separate patch to avoid cluttering this one?
Patch references are like: 9a5d9ba6a363 ("sched/fair: Allow calculate_imbalance() to move idle cpus")
/*
- Check whether the capacity of the rq has been noticeably reduced by side
- activity. The imbalance_pct is used for the threshold.
*/
- Return true is the capacity is reduced
static inline int +check_cpu_capacity(struct rq *rq, struct sched_domain *sd) {
- return ((rq->cpu_capacity * sd->imbalance_pct) <
(rq->cpu_capacity_orig * 100));}
How about cpu_has_capacity() to be consistent with the below function?
This comment could use whitespace:
/*
- group_has_capacity returns true if the group has spare capacity that could
- be used by some tasks.
We consider that a group has spare capacity if the
- number of task is smaller than the number of CPUs or if the usage is lower
- than the available capacity for CFS tasks.
For the latter, we use a
- threshold to stabilize the state, to take into account the variance of the
- tasks' load and to return true if the available capacity in meaningful for
- the load balancer.
As an example, an available capacity of 1% can appear
*/
- but it doesn't make any benefit for the load balance.
+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;
- if (sgs->sum_nr_running < sgs->group_weight)
return true;- return false;
+}
Would it not make sense to first do the nr_running test, its cheaper than the multiplication thing.
+/*
- group_is_overloaded returns true if the group has more tasks than it can
- handle.
We consider that a group is overloaded if the number of tasks is
- greater than the number of CPUs and the tasks already use all available
- capacity for CFS tasks.
For the latter, we use a threshold to stabilize
- the state, to take into account the variance of tasks' load and to return
- true if available capacity is no more meaningful for load balancer
- */
+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;
}
Maybe a note on the difference between group_is_overloaded() and !group_has_capacity()?
As to the comment, I think it can be reduced by referring to the comment of group_has_capacity().
/* * In case the child domain prefers tasks go to siblings
* first, lower the sg capacity 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.
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).group_has_capacity(env, &sds->local_stat) &&(sgs->sum_nr_running > 1)) {sgs->group_no_capacity = 1;sgs->group_type = group_overloaded;}
Looks OK otherwise I suppose.