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charset="utf-8" Load imbalance is observed when the workload frequently forks new threads. Due to CPU affinity, the workload can run on CPU 0-7 in the first group, and only on CPU 8-11 in the second group. CPU 12-15 are always idle. { 0 1 2 3 4 5 6 7 } {8 9 10 11 12 13 14 15} * * * * * * * * * * * * When looking for dst group for newly forked threads, in many times update_sg_wakeup_stats() reports the second group has more idle CPUs than the first group. The scheduler thinks the second group is less busy. Then it selects least busy CPUs among CPU 8-11. Therefore CPU 8-11 can be crowded with newly forked threads, at the same time CPU 0-7 can be idle. A task may not use all the CPUs in a schedule group due to CPU affinity. Only update schedule group statistics for allowed CPUs. Signed-off-by: Adam Li --- Resending this patch from the patchset: https://lore.kernel.org/lkml/20250717062036.432243-2-adamli@os.amperecomput= ing.com/ Only changed commit message. The single patch may be easier for reviewing. --- kernel/sched/fair.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index bc0b7ce8a65d..d5ec15050ebc 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -10671,7 +10671,7 @@ static inline void update_sg_wakeup_stats(struct sc= hed_domain *sd, if (sd->flags & SD_ASYM_CPUCAPACITY) sgs->group_misfit_task_load =3D 1; =20 - for_each_cpu(i, sched_group_span(group)) { + for_each_cpu_and(i, sched_group_span(group), p->cpus_ptr) { struct rq *rq =3D cpu_rq(i); unsigned int local; =20 --=20 2.34.1