Messages in this thread Patch in this message | | | From | Vincent Guittot <> | Subject | [PATCH v4 05/11] sched/fair: use rq->nr_running when balancing load | Date | Fri, 18 Oct 2019 15:26:32 +0200 |
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cfs load_balance only takes care of CFS tasks whereas CPUs can be used by other scheduling class. Typically, a CFS task preempted by a RT or deadline task will not get a chance to be pulled on another CPU because the load_balance doesn't take into account tasks from other classes. Add sum of nr_running in the statistics and use it to detect such situation.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> --- kernel/sched/fair.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 5ae5281..e09fe12b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7704,6 +7704,7 @@ struct sg_lb_stats { unsigned long group_load; /* Total load over the CPUs of the group */ unsigned long group_capacity; unsigned long group_util; /* Total utilization of the group */ + unsigned int sum_nr_running; /* Nr of tasks running in the group */ unsigned int sum_h_nr_running; /* Nr of CFS tasks running in the group */ unsigned int idle_cpus; unsigned int group_weight; @@ -7938,7 +7939,7 @@ static inline int sg_imbalanced(struct sched_group *group) static inline bool group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs) { - if (sgs->sum_h_nr_running < sgs->group_weight) + if (sgs->sum_nr_running < sgs->group_weight) return true; if ((sgs->group_capacity * 100) > @@ -7959,7 +7960,7 @@ group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs) static inline bool group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs) { - if (sgs->sum_h_nr_running <= sgs->group_weight) + if (sgs->sum_nr_running <= sgs->group_weight) return false; if ((sgs->group_capacity * 100) < @@ -8063,6 +8064,8 @@ static inline void update_sg_lb_stats(struct lb_env *env, sgs->sum_h_nr_running += rq->cfs.h_nr_running; nr_running = rq->nr_running; + sgs->sum_nr_running += nr_running; + if (nr_running > 1) *sg_status |= SG_OVERLOAD; @@ -8420,13 +8423,13 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s } if (busiest->group_weight == 1 || sds->prefer_sibling) { - unsigned int nr_diff = busiest->sum_h_nr_running; + unsigned int nr_diff = busiest->sum_nr_running; /* * When prefer sibling, evenly spread running tasks on * groups. */ env->migration_type = migrate_task; - lsub_positive(&nr_diff, local->sum_h_nr_running); + lsub_positive(&nr_diff, local->sum_nr_running); env->imbalance = nr_diff >> 1; return; } @@ -8590,7 +8593,7 @@ static struct sched_group *find_busiest_group(struct lb_env *env) /* Try to move all excess tasks to child's sibling domain */ if (sds.prefer_sibling && local->group_type == group_has_spare && - busiest->sum_h_nr_running > local->sum_h_nr_running + 1) + busiest->sum_nr_running > local->sum_nr_running + 1) goto force_balance; if (busiest->group_type != group_overloaded && -- 2.7.4
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