Re: [PATCH RESEND 3/4] sched/fair: Allow load balancing between CPUs of equal capacity

[Ricardo Neri]

On Wed, Apr 01, 2026 at 09:56:17AM +0100, Christian Loehle wrote:
> On 3/30/26 23:20, Ricardo Neri wrote:
> > sched_balance_find_src_rq() is supposed to avoid picking as busiest a
> > runqueue with a single running task since that would result in the task
> > migrating to a lower-capacity CPU. It also prevents migrations between CPUs
> > of equal capacity.
> > 
> > Migrating tasks between CPUs of equal capacity helps when balancing load in
> > a scheduling domain in which there are CPUs of different capacity and are
> > grouped in clusters of CPUs of equal capacity that share L2 cache. Load
> > should be balanced among these clusters when CONFIG_SCHED_CLUSTER is
> > enabled.
> > 
> > Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
> > ---
> >  kernel/sched/fair.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 3c50ecffa4c7..a7fd4f1f4348 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -11388,6 +11388,7 @@ static struct rq *sched_balance_find_src_rq(struct lb_env *env,
> >  		 * average load.
> >  		 */
> >  		if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
> > +		    capacity_of(env->dst_cpu) != capacity &&
> >  		    !capacity_greater(capacity_of(env->dst_cpu), capacity) &&
> >  		    nr_running == 1)
> >  			continue;
> > 
> 
> For consistency, doesn't it make sense to just invert capacity_greater() here?
> So:
> 
>     capacity_greater(capacity, capacity_of(env->dst_cpu))
>   		if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
>   		    capacity_greater(capacity, capacity_of(env->dst_cpu)) &&
>   		    nr_running == 1)
>   			continue;

Sure! It also makes the code more readable.