[RFC v2 4/9] sched/fair: Don't use CPU marked as avoid for wakeup and load balance
Shrikanth Hegde
sshegde at linux.ibm.com
Thu Jun 26 05:11:03 AEST 2025
Load balancer shouldn't spread CFS tasks into a CPU marked as Avoid.
Remove those CPUs from load balancing decisions.
At wakeup, don't select a CPU marked as avoid.
Signed-off-by: Shrikanth Hegde <sshegde at linux.ibm.com>
---
while tesing didn't see cpu being marked as avoid while new_cpu is.
May need some more probing to see if even cpu can be. if so it could
lead to crash.
kernel/sched/fair.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 7e2963efe800..406288aef535 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8546,7 +8546,12 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
}
rcu_read_unlock();
- return new_cpu;
+ /* Don't select a CPU marked as avoid for wakeup */
+ if (cpu_avoid(new_cpu))
+ return cpu;
+ else
+ return new_cpu;
+
}
/*
@@ -11662,6 +11667,9 @@ static int sched_balance_rq(int this_cpu, struct rq *this_rq,
cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
+ /* Don't spread load into CPUs marked as avoid */
+ cpumask_andnot(cpus, cpus, cpu_avoid_mask);
+
schedstat_inc(sd->lb_count[idle]);
redo:
--
2.43.0
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