sched/fair: Get rid of throttled_lb_pair()

Now that throttled tasks are dequeued and can not stay on rq's cfs_tasks
list, there is no need to take special care of these throttled tasks
anymore in load balance.

Suggested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Aaron Lu <ziqianlu@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Valentin Schneider <vschneid@redhat.com>
Tested-by: Matteo Martelli <matteo.martelli@codethink.co.uk>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://lore.kernel.org/r/20250829081120.806-6-ziqianlu@bytedance.com

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index bdc9bfa0b9efa2b0509409247ad6183f0a00c41f..df8dc389af8e1491b891a31a8c349a197ffdfed2 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5735,23 +5735,6 @@ static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
        return cfs_bandwidth_used() && cfs_rq->throttle_count;
 }
 
-/*
- * Ensure that neither of the group entities corresponding to src_cpu or
- * dest_cpu are members of a throttled hierarchy when performing group
- * load-balance operations.
- */
-static inline int throttled_lb_pair(struct task_group *tg,
-                                   int src_cpu, int dest_cpu)
-{
-       struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
-
-       src_cfs_rq = tg->cfs_rq[src_cpu];
-       dest_cfs_rq = tg->cfs_rq[dest_cpu];
-
-       return throttled_hierarchy(src_cfs_rq) ||
-              throttled_hierarchy(dest_cfs_rq);
-}
-
 static inline bool task_is_throttled(struct task_struct *p)
 {
        return cfs_bandwidth_used() && p->throttled;
@@ -6743,12 +6726,6 @@ static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
        return 0;
 }
 
-static inline int throttled_lb_pair(struct task_group *tg,
-                                   int src_cpu, int dest_cpu)
-{
-       return 0;
-}
-
 #ifdef CONFIG_FAIR_GROUP_SCHED
 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b, struct cfs_bandwidth *parent) {}
 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
@@ -9385,18 +9362,14 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env)
        /*
         * We do not migrate tasks that are:
         * 1) delayed dequeued unless we migrate load, or
-        * 2) throttled_lb_pair, or
-        * 3) cannot be migrated to this CPU due to cpus_ptr, or
-        * 4) running (obviously), or
-        * 5) are cache-hot on their current CPU, or
-        * 6) are blocked on mutexes (if SCHED_PROXY_EXEC is enabled)
+        * 2) cannot be migrated to this CPU due to cpus_ptr, or
+        * 3) running (obviously), or
+        * 4) are cache-hot on their current CPU, or
+        * 5) are blocked on mutexes (if SCHED_PROXY_EXEC is enabled)
         */
        if ((p->se.sched_delayed) && (env->migration_type != migrate_load))
                return 0;
 
-       if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
-               return 0;
-
        /*
         * We want to prioritize the migration of eligible tasks.
         * For ineligible tasks we soft-limit them and only allow