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charset="utf-8" On some platforms, the firmware may expose per-CPU performance differences (e.g., via ACPI CPPC highest_perf) even when the system is effectively symmetric. These small variations, typically due to silicon binning, are reflected in arch_scale_cpu_capacity() and end up being interpreted as real capacity asymmetry. As a result, the scheduler incorrectly enables SD_ASYM_CPUCAPACITY, triggering asymmetry-specific behaviors, even though all CPUs have comparable performance. Prevent this by treating CPU capacities within 20% of the maximum value as equivalent when building the asymmetry topology. This filters out firmware noise, while preserving correct behavior on real heterogeneous systems, where capacity differences are significantly larger. Reported-by: Felix Abecassis Signed-off-by: Andrea Righi --- kernel/sched/topology.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 061f8c85f5552..fe71ea9f3bda7 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -1432,9 +1432,8 @@ static void free_asym_cap_entry(struct rcu_head *head) kfree(entry); } =20 -static inline void asym_cpu_capacity_update_data(int cpu) +static inline void asym_cpu_capacity_update_data(int cpu, unsigned long ca= pacity) { - unsigned long capacity =3D arch_scale_cpu_capacity(cpu); struct asym_cap_data *insert_entry =3D NULL; struct asym_cap_data *entry; =20 @@ -1471,13 +1470,27 @@ static inline void asym_cpu_capacity_update_data(in= t cpu) static void asym_cpu_capacity_scan(void) { struct asym_cap_data *entry, *next; + unsigned long max_cap =3D 0; + unsigned long capacity; int cpu; =20 list_for_each_entry(entry, &asym_cap_list, link) cpumask_clear(cpu_capacity_span(entry)); =20 for_each_cpu_and(cpu, cpu_possible_mask, housekeeping_cpumask(HK_TYPE_DOM= AIN)) - asym_cpu_capacity_update_data(cpu); + max_cap =3D max(max_cap, arch_scale_cpu_capacity(cpu)); + + /* + * Treat small capacity differences (< 20% max capacity) as noise, + * to prevent enabling SD_ASYM_CPUCAPACITY when it's not really + * needed. + */ + for_each_cpu_and(cpu, cpu_possible_mask, housekeeping_cpumask(HK_TYPE_DOM= AIN)) { + capacity =3D arch_scale_cpu_capacity(cpu); + if (capacity * 5 >=3D max_cap * 4) + capacity =3D max_cap; + asym_cpu_capacity_update_data(cpu, capacity); + } =20 list_for_each_entry_safe(entry, next, &asym_cap_list, link) { if (cpumask_empty(cpu_capacity_span(entry))) { --=20 2.53.0