sched/fair: Make group power more consistent

For easier access, less dereferences and more consistent value, store
the group power in update_sg_lb_stats() and use it thereafter. The
actual value in sched_group::sched_group_power::power can change
throughout the load-balance pass if we're unlucky.

Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-739xxqkyvftrhnh9ncudutc7@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 22 insertions, 19 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 57952198b01e..ccf20e76b6b2 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4239,6 +4239,7 @@ struct sg_lb_stats {
         unsigned long group_load; /* Total load over the CPUs of the group */
         unsigned long sum_weighted_load; /* Weighted load of group's tasks */
         unsigned long load_per_task;
+        unsigned long group_power;
         unsigned int sum_nr_running; /* Nr tasks running in the group */
         unsigned int group_capacity;
         unsigned int idle_cpus;
@@ -4518,7 +4519,8 @@ static inline void update_sg_lb_stats(struct lb_env *env,
                 update_group_power(env->sd, env->dst_cpu);
 
         /* Adjust by relative CPU power of the group */
-        sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / group->sgp->power;
+        sgs->group_power = group->sgp->power;
+        sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / sgs->group_power;
 
         /*
          * Consider the group unbalanced when the imbalance is larger
@@ -4537,7 +4539,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
                 sgs->group_imb = 1;
 
         sgs->group_capacity =
-                DIV_ROUND_CLOSEST(group->sgp->power, SCHED_POWER_SCALE);
+                DIV_ROUND_CLOSEST(sgs->group_power, SCHED_POWER_SCALE);
 
         if (!sgs->group_capacity)
                 sgs->group_capacity = fix_small_capacity(env->sd, group);
@@ -4637,7 +4639,7 @@ static inline void update_sd_lb_stats(struct lb_env *env,
 
                 /* Now, start updating sd_lb_stats */
                 sds->total_load += sgs->group_load;
-                sds->total_pwr += sg->sgp->power;
+                sds->total_pwr += sgs->group_power;
 
                 if (!local_group && update_sd_pick_busiest(env, sds, sg, sgs)) {
                         sds->busiest = sg;
@@ -4685,8 +4687,9 @@ static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
         if (env->dst_cpu > busiest_cpu)
                 return 0;
 
-        env->imbalance = DIV_ROUND_CLOSEST(sds->busiest_stat.avg_load *
-                                sds->busiest->sgp->power, SCHED_POWER_SCALE);
+        env->imbalance = DIV_ROUND_CLOSEST(
+                sds->busiest_stat.avg_load * sds->busiest_stat.group_power,
+                SCHED_POWER_SCALE);
 
         return 1;
 }
@@ -4716,7 +4719,7 @@ void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
 
         scaled_busy_load_per_task =
                 (busiest->load_per_task * SCHED_POWER_SCALE) /
-                sds->busiest->sgp->power;
+                busiest->group_power;
 
         if (busiest->avg_load - local->avg_load + scaled_busy_load_per_task >=
             (scaled_busy_load_per_task * imbn)) {
@@ -4730,32 +4733,32 @@ void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
          * moving them.
          */
 
-        pwr_now += sds->busiest->sgp->power *
+        pwr_now += busiest->group_power *
                         min(busiest->load_per_task, busiest->avg_load);
-        pwr_now += sds->local->sgp->power *
+        pwr_now += local->group_power *
                         min(local->load_per_task, local->avg_load);
         pwr_now /= SCHED_POWER_SCALE;
 
         /* Amount of load we'd subtract */
         tmp = (busiest->load_per_task * SCHED_POWER_SCALE) /
-                sds->busiest->sgp->power;
+                busiest->group_power;
         if (busiest->avg_load > tmp) {
-                pwr_move += sds->busiest->sgp->power *
+                pwr_move += busiest->group_power *
                             min(busiest->load_per_task,
                                 busiest->avg_load - tmp);
         }
 
         /* Amount of load we'd add */
-        if (busiest->avg_load * sds->busiest->sgp->power <
+        if (busiest->avg_load * busiest->group_power <
             busiest->load_per_task * SCHED_POWER_SCALE) {
-                tmp = (busiest->avg_load * sds->busiest->sgp->power) /
-                        sds->local->sgp->power;
+                tmp = (busiest->avg_load * busiest->group_power) /
+                      local->group_power;
         } else {
                 tmp = (busiest->load_per_task * SCHED_POWER_SCALE) /
-                        sds->local->sgp->power;
+                      local->group_power;
         }
-        pwr_move += sds->local->sgp->power *
-                        min(local->load_per_task, local->avg_load + tmp);
+        pwr_move += local->group_power *
+                    min(local->load_per_task, local->avg_load + tmp);
         pwr_move /= SCHED_POWER_SCALE;
 
         /* Move if we gain throughput */
@@ -4800,7 +4803,7 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
                         (busiest->sum_nr_running - busiest->group_capacity);
 
                 load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
-                load_above_capacity /= sds->busiest->sgp->power;
+                load_above_capacity /= busiest->group_power;
         }
 
         /*
@@ -4818,8 +4821,8 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
 
         /* How much load to actually move to equalise the imbalance */
         env->imbalance = min(
-                max_pull * sds->busiest->sgp->power,
-                (sds->avg_load - local->avg_load) * sds->local->sgp->power
+                max_pull * busiest->group_power,
+                (sds->avg_load - local->avg_load) * local->group_power
         ) / SCHED_POWER_SCALE;
 
         /*