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

[Shrikanth Hegde]

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@xxxxxxxxxxxxx>
> > ---
> >   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