sched/balancing: Simplify the sg_status bitmask and use separate ->overloaded and...

SG_OVERLOADED and SG_OVERUTILIZED flags plus the sg_status bitmask are an
unnecessary complication that only make the code harder to read and slower.

We only ever set them separately:

 thule:~/tip> git grep SG_OVER kernel/sched/
 kernel/sched/fair.c:            set_rd_overutilized_status(rq->rd, SG_OVERUTILIZED);
 kernel/sched/fair.c:                    *sg_status |= SG_OVERLOADED;
 kernel/sched/fair.c:                    *sg_status |= SG_OVERUTILIZED;
 kernel/sched/fair.c:                            *sg_status |= SG_OVERLOADED;
 kernel/sched/fair.c:            set_rd_overloaded(env->dst_rq->rd, sg_status & SG_OVERLOADED);
 kernel/sched/fair.c:                                       sg_status & SG_OVERUTILIZED);
 kernel/sched/fair.c:    } else if (sg_status & SG_OVERUTILIZED) {
 kernel/sched/fair.c:            set_rd_overutilized_status(env->dst_rq->rd, SG_OVERUTILIZED);
 kernel/sched/sched.h:#define SG_OVERLOADED              0x1 /* More than one runnable task on a CPU. */
 kernel/sched/sched.h:#define SG_OVERUTILIZED            0x2 /* One or more CPUs are over-utilized. */
 kernel/sched/sched.h:           set_rd_overloaded(rq->rd, SG_OVERLOADED);

And use them separately, which results in suboptimal code:

                /* update overload indicator if we are at root domain */
                set_rd_overloaded(env->dst_rq->rd, sg_status & SG_OVERLOADED);

                /* Update over-utilization (tipping point, U >= 0) indicator */
                set_rd_overutilized_status(env->dst_rq->rd,

Introduce separate sg_overloaded and sg_overutilized flags in update_sd_lb_stats()
and its lower level functions, and change all of them to 'bool'.

Remove the now unused SG_OVERLOADED and SG_OVERUTILIZED flags.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Tested-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Cc: Qais Yousef <qyousef@layalina.io>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/ZgVPhODZ8/nbsqbP@gmail.com

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f29efd5f19f67e52006524607d0af4c28f542cdc..1dd37168da50e8ace7d75cdd38338c3a81a18e4f 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6688,19 +6688,18 @@ static inline bool cpu_overutilized(int cpu)
 /*
  * overutilized value make sense only if EAS is enabled
  */
-static inline int is_rd_overutilized(struct root_domain *rd)
+static inline bool is_rd_overutilized(struct root_domain *rd)
 {
        return !sched_energy_enabled() || READ_ONCE(rd->overutilized);
 }
 
-static inline void set_rd_overutilized(struct root_domain *rd,
-                                             unsigned int status)
+static inline void set_rd_overutilized(struct root_domain *rd, bool flag)
 {
        if (!sched_energy_enabled())
                return;
 
-       WRITE_ONCE(rd->overutilized, status);
-       trace_sched_overutilized_tp(rd, !!status);
+       WRITE_ONCE(rd->overutilized, flag);
+       trace_sched_overutilized_tp(rd, flag);
 }
 
 static inline void check_update_overutilized_status(struct rq *rq)
@@ -6711,7 +6710,7 @@ static inline void check_update_overutilized_status(struct rq *rq)
         */
 
        if (!is_rd_overutilized(rq->rd) && cpu_overutilized(rq->cpu))
-               set_rd_overutilized(rq->rd, SG_OVERUTILIZED);
+               set_rd_overutilized(rq->rd, 1);
 }
 #else
 static inline void check_update_overutilized_status(struct rq *rq) { }
@@ -9934,13 +9933,15 @@ sched_reduced_capacity(struct rq *rq, struct sched_domain *sd)
  * @sds: Load-balancing data with statistics of the local group.
  * @group: sched_group whose statistics are to be updated.
  * @sgs: variable to hold the statistics for this group.
- * @sg_status: Holds flag indicating the status of the sched_group
+ * @sg_overloaded: sched_group is overloaded
+ * @sg_overutilized: sched_group is overutilized
  */
 static inline void update_sg_lb_stats(struct lb_env *env,
                                      struct sd_lb_stats *sds,
                                      struct sched_group *group,
                                      struct sg_lb_stats *sgs,
-                                     int *sg_status)
+                                     bool *sg_overloaded,
+                                     bool *sg_overutilized)
 {
        int i, nr_running, local_group;
 
@@ -9961,10 +9962,10 @@ static inline void update_sg_lb_stats(struct lb_env *env,
                sgs->sum_nr_running += nr_running;
 
                if (nr_running > 1)
-                       *sg_status |= SG_OVERLOADED;
+                       *sg_overloaded = 1;
 
                if (cpu_overutilized(i))
-                       *sg_status |= SG_OVERUTILIZED;
+                       *sg_overutilized = 1;
 
 #ifdef CONFIG_NUMA_BALANCING
                sgs->nr_numa_running += rq->nr_numa_running;
@@ -9986,7 +9987,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
                        /* Check for a misfit task on the cpu */
                        if (sgs->group_misfit_task_load < rq->misfit_task_load) {
                                sgs->group_misfit_task_load = rq->misfit_task_load;
-                               *sg_status |= SG_OVERLOADED;
+                               *sg_overloaded = 1;
                        }
                } else if (env->idle && sched_reduced_capacity(rq, env->sd)) {
                        /* Check for a task running on a CPU with reduced capacity */
@@ -10612,7 +10613,7 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
        struct sg_lb_stats *local = &sds->local_stat;
        struct sg_lb_stats tmp_sgs;
        unsigned long sum_util = 0;
-       int sg_status = 0;
+       bool sg_overloaded = 0, sg_overutilized = 0;
 
        do {
                struct sg_lb_stats *sgs = &tmp_sgs;
@@ -10628,7 +10629,7 @@ 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, sds, sg, sgs, &sg_status);
+               update_sg_lb_stats(env, sds, sg, sgs, &sg_overloaded, &sg_overutilized);
 
                if (!local_group && update_sd_pick_busiest(env, sds, sg, sgs)) {
                        sds->busiest = sg;
@@ -10657,13 +10658,12 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
 
        if (!env->sd->parent) {
                /* update overload indicator if we are at root domain */
-               set_rd_overloaded(env->dst_rq->rd, sg_status & SG_OVERLOADED);
+               set_rd_overloaded(env->dst_rq->rd, sg_overloaded);
 
                /* Update over-utilization (tipping point, U >= 0) indicator */
-               set_rd_overutilized(env->dst_rq->rd,
-                                          sg_status & SG_OVERUTILIZED);
-       } else if (sg_status & SG_OVERUTILIZED) {
-               set_rd_overutilized(env->dst_rq->rd, SG_OVERUTILIZED);
+               set_rd_overutilized(env->dst_rq->rd, sg_overloaded);
+       } else if (sg_overutilized) {
+               set_rd_overutilized(env->dst_rq->rd, sg_overutilized);
        }
 
        update_idle_cpu_scan(env, sum_util);

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 07c6669b8250b9f68c74ffa975386a028c7304e1..7c39dbf31f750cb7d92f49c547abfaff5a79f894 100644 (file)
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -713,7 +713,7 @@ struct rt_rq {
        } highest_prio;
 #endif
 #ifdef CONFIG_SMP
-       int                     overloaded;
+       bool                    overloaded;
        struct plist_head       pushable_tasks;
 
 #endif /* CONFIG_SMP */
@@ -757,7 +757,7 @@ struct dl_rq {
                u64             next;
        } earliest_dl;
 
-       int                     overloaded;
+       bool                    overloaded;
 
        /*
         * Tasks on this rq that can be pushed away. They are kept in
@@ -850,10 +850,6 @@ struct perf_domain {
        struct rcu_head rcu;
 };
 
-/* Scheduling group status flags */
-#define SG_OVERLOADED          0x1 /* More than one runnable task on a CPU. */
-#define SG_OVERUTILIZED                0x2 /* One or more CPUs are over-utilized. */
-
 /*
  * We add the notion of a root-domain which will be used to define per-domain
  * variables. Each exclusive cpuset essentially defines an island domain by
@@ -874,10 +870,10 @@ struct root_domain {
         * - More than one runnable task
         * - Running task is misfit
         */
-       int                     overloaded;
+       bool                    overloaded;
 
        /* Indicate one or more cpus over-utilized (tipping point) */
-       int                     overutilized;
+       bool                    overutilized;
 
        /*
         * The bit corresponding to a CPU gets set here if such CPU has more
@@ -2540,9 +2536,8 @@ static inline void add_nr_running(struct rq *rq, unsigned count)
        }
 
 #ifdef CONFIG_SMP
-       if (prev_nr < 2 && rq->nr_running >= 2) {
-               set_rd_overloaded(rq->rd, SG_OVERLOADED);
-       }
+       if (prev_nr < 2 && rq->nr_running >= 2)
+               set_rd_overloaded(rq->rd, 1);
 #endif
 
        sched_update_tick_dependency(rq);