Re: [RFC PATCH v4 08/12] sched: Add over-utilization/tipping point indicator

[Peter Zijlstra]

On Thu, Jun 28, 2018 at 12:40:39PM +0100, Quentin Perret wrote:
>  static inline void update_sg_lb_stats(struct lb_env *env,
>                       struct sched_group *group, int load_idx,
>                       int local_group, struct sg_lb_stats *sgs,
> -                     bool *overload)
> +                     bool *overload, int *overutilized)

> @@ -8308,7 +8336,7 @@ static inline void update_sd_lb_stats(struct lb_env 
> *env, struct sd_lb_stats *sd
>               }
>  
>               update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
> -                                             &overload);
> +                                             &overload, &overutilized);
>  
>               if (local_group)
>                       goto next_group;

I'm thinking maybe we should reduce arguments here a little.

@load_idx and @local_group look to be trivially computable..

and possibly we could frob overload and overutilized in a single
variable with some flags?


diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 321cd5dcf2e8..091859069620 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8114,10 +8114,12 @@ static bool update_nohz_stats(struct rq *rq, bool force)
  * @overload: Indicate more than one runnable task for any CPU.
  */
 static inline void update_sg_lb_stats(struct lb_env *env,
-                       struct sched_group *group, int load_idx,
-                       int local_group, struct sg_lb_stats *sgs,
+                       struct sched_group *group,
+                       struct sg_lb_stats *sgs,
                        bool *overload)
 {
+       int local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sd));
+       int load_idx = get_sd_load_idx(env->sd, env->idle);
        unsigned long load;
        int i, nr_running;
 
@@ -8278,7 +8280,7 @@ static inline void update_sd_lb_stats(struct lb_env *env, 
struct sd_lb_stats *sd
        struct sched_group *sg = env->sd->groups;
        struct sg_lb_stats *local = &sds->local_stat;
        struct sg_lb_stats tmp_sgs;
-       int load_idx, prefer_sibling = 0;
+       int prefer_sibling = 0;
        bool overload = false;
 
        if (child && child->flags & SD_PREFER_SIBLING)
@@ -8289,8 +8291,6 @@ static inline void update_sd_lb_stats(struct lb_env *env, 
struct sd_lb_stats *sd
                env->flags |= LBF_NOHZ_STATS;
 #endif
 
-       load_idx = get_sd_load_idx(env->sd, env->idle);
-
        do {
                struct sg_lb_stats *sgs = &tmp_sgs;
                int local_group;
@@ -8305,8 +8305,7 @@ static inline void update_sd_lb_stats(struct lb_env *env, 
struct sd_lb_stats *sd
                                update_group_capacity(env->sd, env->dst_cpu);
                }
 
-               update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
-                                               &overload);
+               update_sg_lb_stats(env, sg, sgs, &overload);
 
                if (local_group)
                        goto next_group;