Hello Chenyu, Venkat,
On 5/25/2026 9:05 PM, Chen, Yu C wrote:
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 3467f86fd78f..cf6c2e4190ab 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -1042,11 +1042,6 @@ static const struct cpumask
> *tl_smallcore_smt_mask(struct sched_domain_topology_
> }
> #endif
>
> -struct cpumask *cpu_coregroup_mask(int cpu)
> -{
> - return per_cpu(cpu_coregroup_map, cpu);
> -}
> -
> static bool has_coregroup_support(void)
> {
> /* Coregroup identification not available on shared systems */
> @@ -1056,6 +1051,14 @@ static bool has_coregroup_support(void)
> return coregroup_enabled;
> }
>
> +struct cpumask *cpu_coregroup_mask(int cpu)
> +{
> + if (!has_coregroup_support())
> + return cpu_l2_cache_mask(cpu);
> +> + return per_cpu(cpu_coregroup_map, cpu);
Interestingly, on powerpc, the MC domain doesn't have SD_SHARE_LLC flag
set but I believe there is still some benefit of keeping the tasks on
the same hemisphere?
If we are actually aiming for LLC, I think cpu_l2_cache_mask() is the
right cpumask for all cases since tl_cache_mask() also returns that
and the l2_cache_mask is set in all cases covered by update_mask_by_l2()
in the same file.
If consolidation on hemisphere is beneficial, then the above diff
looks correct.
Note: For has_coregroup_support(), with the above fix, the scheduler
side llc_id will now be based on MC domain's span which seems wrong
since it doesn't have SD_SHARE_LLC flag and might lead to other
behavioral changes now.
> +}
> +
> static int __init init_big_cores(void)
> {
> int cpu;
--
Thanks and Regards,
Prateek
