Commit c59862f8 authored by Vincent Guittot's avatar Vincent Guittot Committed by Peter Zijlstra
Browse files

sched/fair: Cleanup loop_max and loop_break 



sched_nr_migrate_break is set to a fix value and never changes so we can
replace it by a define SCHED_NR_MIGRATE_BREAK.

Also, we adjust SCHED_NR_MIGRATE_BREAK to be aligned with the init value
of sysctl_sched_nr_migrate which can be init to different values.

Then, use SCHED_NR_MIGRATE_BREAK to init sysctl_sched_nr_migrate.

The behavior stays unchanged unless you modify sysctl_sched_nr_migrate
trough debugfs.

Signed-off-by: default avatarVincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220825122726.20819-3-vincent.guittot@linaro.org
parent b0defa7a

kernel/sched/core.c

+1 −5
Original line number Diff line number Diff line
@@ -142,11 +142,7 @@ __read_mostly int sysctl_resched_latency_warn_once = 1; 
 * Number of tasks to iterate in a single balance run.

 * Limited because this is done with IRQs disabled.

 */

#ifdef CONFIG_PREEMPT_RT

const_debug unsigned int sysctl_sched_nr_migrate = 8;

#else

const_debug unsigned int sysctl_sched_nr_migrate = 32;

#endif

const_debug unsigned int sysctl_sched_nr_migrate = SCHED_NR_MIGRATE_BREAK;



__read_mostly int scheduler_running;

kernel/sched/fair.c

+4 −7
Original line number Diff line number Diff line
@@ -8009,8 +8009,6 @@ static struct task_struct *detach_one_task(struct lb_env *env) 
	return NULL;

}



static const unsigned int sched_nr_migrate_break = 32;



/*

 * detach_tasks() -- tries to detach up to imbalance load/util/tasks from

 * busiest_rq, as part of a balancing operation within domain "sd".
@@ -8059,7 +8057,7 @@ static int detach_tasks(struct lb_env *env) 


		/* take a breather every nr_migrate tasks */

		if (env->loop > env->loop_break) {

			env->loop_break += sched_nr_migrate_break;

			env->loop_break += SCHED_NR_MIGRATE_BREAK;

			env->flags |= LBF_NEED_BREAK;

			break;

		}
@@ -10100,14 +10098,13 @@ static int load_balance(int this_cpu, struct rq *this_rq, 
	struct rq *busiest;

	struct rq_flags rf;

	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);



	struct lb_env env = {

		.sd		= sd,

		.dst_cpu	= this_cpu,

		.dst_rq		= this_rq,

		.dst_grpmask    = sched_group_span(sd->groups),

		.idle		= idle,

		.loop_break	= sched_nr_migrate_break,

		.loop_break	= SCHED_NR_MIGRATE_BREAK,

		.cpus		= cpus,

		.fbq_type	= all,

		.tasks		= LIST_HEAD_INIT(env.tasks),
@@ -10216,7 +10213,7 @@ static int load_balance(int this_cpu, struct rq *this_rq, 
			env.dst_cpu	 = env.new_dst_cpu;

			env.flags	&= ~LBF_DST_PINNED;

			env.loop	 = 0;

			env.loop_break	 = sched_nr_migrate_break;

			env.loop_break	 = SCHED_NR_MIGRATE_BREAK;



			/*

			 * Go back to "more_balance" rather than "redo" since we
@@ -10248,7 +10245,7 @@ static int load_balance(int this_cpu, struct rq *this_rq, 
			 */

			if (!cpumask_subset(cpus, env.dst_grpmask)) {

				env.loop = 0;

				env.loop_break = sched_nr_migrate_break;

				env.loop_break = SCHED_NR_MIGRATE_BREAK;

				goto redo;

			}

			goto out_all_pinned;

kernel/sched/sched.h

+6 −0
Original line number Diff line number Diff line
@@ -2423,6 +2423,12 @@ extern void deactivate_task(struct rq *rq, struct task_struct *p, int flags); 


extern void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags);



#ifdef CONFIG_PREEMPT_RT

#define SCHED_NR_MIGRATE_BREAK 8

#else

#define SCHED_NR_MIGRATE_BREAK 32

#endif



extern const_debug unsigned int sysctl_sched_nr_migrate;

extern const_debug unsigned int sysctl_sched_migration_cost;