Re: [PATCH 3/3] arm64/sched: Enable CPPC-based asympacking

[Valentin Schneider]

On 25/03/26 18:13, Christian Loehle wrote:
> @@ -1753,7 +1760,7 @@ static inline int topology_arch_sched_asym_flags(void)
>  #ifdef CONFIG_SCHED_SMT
>  int cpu_smt_flags(void)
>  {
> -	return SD_SHARE_CPUCAPACITY | SD_SHARE_LLC;
> +	return SD_SHARE_CPUCAPACITY | SD_SHARE_LLC | arch_sched_asym_flags();
>  }
>  
>  const struct cpumask *tl_smt_mask(struct sched_domain_topology_level *tl, int cpu)
> @@ -1765,7 +1772,7 @@ const struct cpumask *tl_smt_mask(struct sched_domain_topology_level *tl, int cp
>  #ifdef CONFIG_SCHED_CLUSTER
>  int cpu_cluster_flags(void)
>  {
> -	return SD_CLUSTER | SD_SHARE_LLC;
> +	return SD_CLUSTER | SD_SHARE_LLC | arch_sched_asym_flags();
>  }
>  
>  const struct cpumask *tl_cls_mask(struct sched_domain_topology_level *tl, int cpu)
> @@ -1777,7 +1784,7 @@ const struct cpumask *tl_cls_mask(struct sched_domain_topology_level *tl, int cp
>  #ifdef CONFIG_SCHED_MC
>  int cpu_core_flags(void)
>  {
> -	return SD_SHARE_LLC;
> +	return SD_SHARE_LLC | arch_sched_asym_flags();
>  }
>

So while the binning problem applies to more than one architecture, I'm not
sure we want this to be generally applied to all topology levels. This is
/technically/ not a problem since even if a topology level has
SD_ASYM_PACKING, all CPUs at that level can have the same priority, but
in that case it's a bit wasteful.

I don't have any better ideas ATM to keep this arch-specific via
set_sched_topology(), like how x86 and powerpc handle asym packing.