Commit d3d663fa authored by Vincent Guittot's avatar Vincent Guittot Committed by Peter Zijlstra
Browse files

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: default avatarVincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: default avatarPierre Gondois <pierre.gondois@arm.com>
Link: https://patch.msgid.link/20260206095454.1520619-1-vincent.guittot@linaro.org
parent 92647580

kernel/sched/fair.c

+13 −5
Original line number Diff line number Diff line
@@ -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;