[RFC PATCH v2 5/7] sched/fair: get rid of throttled_lb_pair()

Aaron Lu
2025-04-09T12:08:38Z

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>
---
kernel/sched/fair.c | 33 +++------------------------------
1 file changed, 3 insertions(+), 30 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 76b8a5ffcbdd2..ff4252995d677 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5808,23 +5808,6 @@ 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 !list_empty(&p->throttle_node);
@@ -6742,12 +6725,6 @@ 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) {}
@@ -9377,17 +9354,13 @@ 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.
+ * 2) cannot be migrated to this CPU due to cpus_ptr, or
+ * 3) running (obviously), or
+ * 4) are cache-hot on their current CPU.
*/
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
--
2.39.5