From d3d663faa1d4e86491b77ab72eabc3ea2f58b197 Mon Sep 17 00:00:00 2001 From: Vincent Guittot Date: Fri, 6 Feb 2026 10:54:54 +0100 Subject: [PATCH] sched/fair: Filter false overloaded_group case for EAS With EAS, a group should be set overloaded if at least 1 CPU in the group is overutilized but it can happen that a CPU is fully utilized by tasks because of clamping the compute capacity of the CPU. In such case, the CPU is not overutilized and as a result should not be set overloaded as well. group_overloaded being a higher priority than group_misfit, such group can be selected as the busiest group instead of a group with a mistfit task and prevents load_balance to select the CPU with the misfit task to pull the latter on a fitting CPU. Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Tested-by: Pierre Gondois Link: https://patch.msgid.link/20260206095454.1520619-1-vincent.guittot@linaro.org --- kernel/sched/fair.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index b8b052b2149b7..966e252822154 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -10211,6 +10211,7 @@ struct sg_lb_stats { unsigned int group_asym_packing; /* Tasks should be moved to preferred CPU */ unsigned int group_smt_balance; /* Task on busy SMT be moved */ unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */ + unsigned int group_overutilized; /* At least one CPU is overutilized in the group */ #ifdef CONFIG_NUMA_BALANCING unsigned int nr_numa_running; unsigned int nr_preferred_running; @@ -10443,6 +10444,13 @@ group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs) static inline bool group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs) { + /* + * With EAS and uclamp, 1 CPU in the group must be overutilized to + * consider the group overloaded. + */ + if (sched_energy_enabled() && !sgs->group_overutilized) + return false; + if (sgs->sum_nr_running <= sgs->group_weight) return false; @@ -10626,14 +10634,12 @@ sched_reduced_capacity(struct rq *rq, struct sched_domain *sd) * @group: sched_group whose statistics are to be updated. * @sgs: variable to hold the statistics for this group. * @sg_overloaded: sched_group is overloaded - * @sg_overutilized: sched_group is overutilized */ static inline void update_sg_lb_stats(struct lb_env *env, struct sd_lb_stats *sds, struct sched_group *group, struct sg_lb_stats *sgs, - bool *sg_overloaded, - bool *sg_overutilized) + bool *sg_overloaded) { int i, nr_running, local_group, sd_flags = env->sd->flags; bool balancing_at_rd = !env->sd->parent; @@ -10655,7 +10661,7 @@ static inline void update_sg_lb_stats(struct lb_env *env, sgs->sum_nr_running += nr_running; if (cpu_overutilized(i)) - *sg_overutilized = 1; + sgs->group_overutilized = 1; /* * No need to call idle_cpu() if nr_running is not 0 @@ -11326,13 +11332,15 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd update_group_capacity(env->sd, env->dst_cpu); } - update_sg_lb_stats(env, sds, sg, sgs, &sg_overloaded, &sg_overutilized); + update_sg_lb_stats(env, sds, sg, sgs, &sg_overloaded); if (!local_group && update_sd_pick_busiest(env, sds, sg, sgs)) { sds->busiest = sg; sds->busiest_stat = *sgs; } + sg_overutilized |= sgs->group_overutilized; + /* Now, start updating sd_lb_stats */ sds->total_load += sgs->group_load; sds->total_capacity += sgs->group_capacity; -- 2.47.3