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>> -} >> - >>  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? > You are right. I guess power9 reported here does not have hemisphere and power10 has, according to commit fb2ff9fa72e2: "From Power10 processors onwards, each chip has 2 hemispheres" but yes on both power9 and power10, MC domain doesn't have SD_SHARE_LLC thus aggregating threads to 1 L2 domain might bring benefit. A side note is that, cache aware scheduling is disabled on power for now because power does not use the generic cacheinfo framework, thus its cache size is returned as 0 so get_effective_llc_bytes() returns 0(for now, unless we get the help from IBM friends to support it) commit 7030513a0877 ("7030513a0877") > 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. > You are right, it seems to be a bug when has_coregroup_support() is enabled. Maybe we can always return l2 id for power? How about this(revert previous diff): diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm/topology.h index 66ed5fe1b718..3b3b4156f418 100644 --- a/arch/powerpc/include/asm/topology.h +++ b/arch/powerpc/include/asm/topology.h @@ -130,13 +130,15 @@ static inline int cpu_to_coregroup_id(int cpu) #ifdef CONFIG_SMP #include +#include struct cpumask *cpu_coregroup_mask(int cpu); const struct cpumask *cpu_die_mask(int cpu); int cpu_die_id(int cpu); +#define arch_llc_mask(cpu) cpu_l2_cache_mask(cpu) + #ifdef CONFIG_PPC64 -#include #define topology_physical_package_id(cpu) (cpu_to_chip_id(cpu)) #define topology_sibling_cpumask(cpu) (per_cpu(cpu_sibling_map, cpu)) diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index df2ceb54c970..6772eb0ce493 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -2063,12 +2063,18 @@ const struct cpumask *tl_mc_mask(struct sched_domain_topology_level *tl, int cpu return cpu_coregroup_mask(cpu); } -#define llc_mask(cpu) cpu_coregroup_mask(cpu) +#ifndef arch_llc_mask +#define arch_llc_mask(cpu) cpu_coregroup_mask(cpu) +#endif #else -#define llc_mask(cpu) cpumask_of(cpu) +#ifndef arch_llc_mask +#define arch_llc_mask(cpu) cpumask_of(cpu) +#endif #endif +#define llc_mask(cpu) arch_llc_mask(cpu) + const struct cpumask *tl_pkg_mask(struct sched_domain_topology_level *tl, int cpu) { return cpu_node_mask(cpu); thanks, Chenyu >> +} >> + >>  static int __init init_big_cores(void) >>  { >>         int cpu; >