sched/fair: Rework sched_use_asym_prio() and sched_asym_prefer()

sched_use_asym_prio() and sched_asym_prefer() are used together in various
places. Consolidate them into a single function sched_asym().

The existing sched_asym() function is only used when collecting statistics
of a scheduling group. Rename it as sched_group_asym(), and remove the
obsolete function description.

This makes the code easier to read. No functional changes.

Signed-off-by: Alex Shi <alexs@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Reviewed-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20240210113924.1130448-3-alexs@kernel.org

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 300d1bfe6d2bfbaa549f37667f93cf693f920620..475e2ca66b6324fa1d4d07255650accefba1a5cc 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9750,8 +9750,18 @@ static bool sched_use_asym_prio(struct sched_domain *sd, int cpu)
        return sd->flags & SD_SHARE_CPUCAPACITY || is_core_idle(cpu);
 }
 
+static inline bool sched_asym(struct sched_domain *sd, int dst_cpu, int src_cpu)
+{
+       /*
+        * First check if @dst_cpu can do asym_packing load balance. Only do it
+        * if it has higher priority than @src_cpu.
+        */
+       return sched_use_asym_prio(sd, dst_cpu) &&
+               sched_asym_prefer(dst_cpu, src_cpu);
+}
+
 /**
- * sched_asym - Check if the destination CPU can do asym_packing load balance
+ * sched_group_asym - Check if the destination CPU can do asym_packing balance
  * @env:       The load balancing environment
  * @sgs:       Load-balancing statistics of the candidate busiest group
  * @group:     The candidate busiest group
@@ -9759,34 +9769,21 @@ static bool sched_use_asym_prio(struct sched_domain *sd, int cpu)
  * @env::dst_cpu can do asym_packing if it has higher priority than the
  * preferred CPU of @group.
  *
- * SMT is a special case. If we are balancing load between cores, @env::dst_cpu
- * can do asym_packing balance only if all its SMT siblings are idle. Also, it
- * can only do it if @group is an SMT group and has exactly on busy CPU. Larger
- * imbalances in the number of CPUS are dealt with in find_busiest_group().
- *
- * If we are balancing load within an SMT core, or at PKG domain level, always
- * proceed.
- *
  * Return: true if @env::dst_cpu can do with asym_packing load balance. False
  * otherwise.
  */
 static inline bool
-sched_asym(struct lb_env *env, struct sg_lb_stats *sgs, struct sched_group *group)
+sched_group_asym(struct lb_env *env, struct sg_lb_stats *sgs, struct sched_group *group)
 {
-       /* Ensure that the whole local core is idle, if applicable. */
-       if (!sched_use_asym_prio(env->sd, env->dst_cpu))
-               return false;
-
        /*
-        * CPU priorities does not make sense for SMT cores with more than one
+        * CPU priorities do not make sense for SMT cores with more than one
         * busy sibling.
         */
-       if (group->flags & SD_SHARE_CPUCAPACITY) {
-               if (sgs->group_weight - sgs->idle_cpus != 1)
-                       return false;
-       }
+       if ((group->flags & SD_SHARE_CPUCAPACITY) &&
+           (sgs->group_weight - sgs->idle_cpus != 1))
+               return false;
 
-       return sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu);
+       return sched_asym(env->sd, env->dst_cpu, group->asym_prefer_cpu);
 }
 
 /* One group has more than one SMT CPU while the other group does not */
@@ -9942,7 +9939,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
        /* Check if dst CPU is idle and preferred to this group */
        if (!local_group && env->sd->flags & SD_ASYM_PACKING &&
            env->idle != CPU_NOT_IDLE && sgs->sum_h_nr_running &&
-           sched_asym(env, sgs, group)) {
+           sched_group_asym(env, sgs, group)) {
                sgs->group_asym_packing = 1;
        }
 
@@ -11028,8 +11025,7 @@ static struct rq *find_busiest_queue(struct lb_env *env,
                 * SMT cores with more than one busy sibling.
                 */
                if ((env->sd->flags & SD_ASYM_PACKING) &&
-                   sched_use_asym_prio(env->sd, i) &&
-                   sched_asym_prefer(i, env->dst_cpu) &&
+                   sched_asym(env->sd, i, env->dst_cpu) &&
                    nr_running == 1)
                        continue;
 
@@ -11899,8 +11895,7 @@ static void nohz_balancer_kick(struct rq *rq)
                 * preferred CPU must be idle.
                 */
                for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) {
-                       if (sched_use_asym_prio(sd, i) &&
-                           sched_asym_prefer(i, cpu)) {
+                       if (sched_asym(sd, i, cpu)) {
                                flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
                                goto unlock;
                        }