On 6/26/25 05:32, Yury Norov wrote:
> On Thu, Jun 26, 2025 at 12:41:03AM +0530, Shrikanth Hegde wrote:
>> 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@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;
>> +
>> }
>
> There are more 'return's in this function, but you patch only one...
I had seen it but forgot to add. (since eas wasn't enabled in the system
so i forgot)
>
>>
>> /*
>> @@ -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