Re: [PATCH v6 06/23] sched/fair: Load balance only among preferred CPUs

[Shrikanth Hegde <sshegde@linux.ibm.com>]

On 7/1/26 9:49 PM, Yury Norov wrote:
> On Wed, Jul 01, 2026 at 07:46:37PM +0530, Shrikanth Hegde wrote:
>> Consider only preferred CPUs for load balance.
>>
>> With this, load balance will end up choosing a preferred CPUs for pull.
>> This makes it not fight against the push task mechanism which happens
>> at tick. Also, this stops active balance to happen on non-preferred CPU
>> pulling the load.
>>
>> This means there is no load balancing if the task is pinned only to
>> non-preferred CPUs. They will continue to run where they were previously
>> running before the CPUs was marked as non-preferred.
>>
>> Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
>> ---
>>   kernel/sched/fair.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index ce05acf52d35..9b2931b559d6 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -13391,7 +13391,8 @@ static int sched_balance_rq(int this_cpu, struct rq *this_rq,
>>   	};
>>   	bool need_unlock = false;
>>   
>> -	cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
>> +	/* Spread load among preferred CPUs */
> 
> We don't have a "Spread load among active CPUs" comment. Don't think
> it's more difficult to understand what happens if you replace one mask
> with another.
> 

Alright, I will drop it.

>> +	cpumask_and(cpus, sched_domain_span(sd), cpu_preferred_mask);
>>   
>>   	schedstat_inc(sd->lb_count[idle]);
>>   
>> -- 
>> 2.47.3