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sched/fair: Cleanup loop_max and loop_break

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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: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220825122726.20819-3-vincent.guittot@linaro.org
This commit is contained in:
Vincent Guittot 2022-08-25 14:27:24 +02:00 committed by Peter Zijlstra
parent b0defa7ae0
commit c59862f826
3 changed files with 11 additions and 12 deletions
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6
kernel/sched/core.c
View File

@ -142,11 +142,7 @@ __read_mostly int sysctl_resched_latency_warn_once = 1;
* Number of tasks to iterate in a single balance run. * Number of tasks to iterate in a single balance run.
* Limited because this is done with IRQs disabled. * Limited because this is done with IRQs disabled.
*/ */
#ifdef CONFIG_PREEMPT_RT const_debug unsigned int sysctl_sched_nr_migrate = SCHED_NR_MIGRATE_BREAK;
const_debug unsigned int sysctl_sched_nr_migrate = 8;
#else
const_debug unsigned int sysctl_sched_nr_migrate = 32;
#endif
__read_mostly int scheduler_running; __read_mostly int scheduler_running;

11
kernel/sched/fair.c
View File

@ -8009,8 +8009,6 @@ static struct task_struct *detach_one_task(struct lb_env *env)
return NULL; return NULL;
} }
static const unsigned int sched_nr_migrate_break = 32;
/* /*
* detach_tasks() -- tries to detach up to imbalance load/util/tasks from * detach_tasks() -- tries to detach up to imbalance load/util/tasks from
* busiest_rq, as part of a balancing operation within domain "sd". * 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 */ /* take a breather every nr_migrate tasks */
if (env->loop > env->loop_break) { 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; env->flags |= LBF_NEED_BREAK;
break; break;
} }
@ -10100,14 +10098,13 @@ static int load_balance(int this_cpu, struct rq *this_rq,
struct rq *busiest; struct rq *busiest;
struct rq_flags rf; struct rq_flags rf;
struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask); struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
struct lb_env env = { struct lb_env env = {
.sd = sd, .sd = sd,
.dst_cpu = this_cpu, .dst_cpu = this_cpu,
.dst_rq = this_rq, .dst_rq = this_rq,
.dst_grpmask = sched_group_span(sd->groups), .dst_grpmask = sched_group_span(sd->groups),
.idle = idle, .idle = idle,
.loop_break = sched_nr_migrate_break, .loop_break = SCHED_NR_MIGRATE_BREAK,
.cpus = cpus, .cpus = cpus,
.fbq_type = all, .fbq_type = all,
.tasks = LIST_HEAD_INIT(env.tasks), .tasks = LIST_HEAD_INIT(env.tasks),
@ -10216,7 +10213,7 @@ more_balance:
env.dst_cpu = env.new_dst_cpu; env.dst_cpu = env.new_dst_cpu;
env.flags &= ~LBF_DST_PINNED; env.flags &= ~LBF_DST_PINNED;
env.loop = 0; 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 * Go back to "more_balance" rather than "redo" since we
@ -10248,7 +10245,7 @@ more_balance:
*/ */
if (!cpumask_subset(cpus, env.dst_grpmask)) { if (!cpumask_subset(cpus, env.dst_grpmask)) {
env.loop = 0; env.loop = 0;
env.loop_break = sched_nr_migrate_break; env.loop_break = SCHED_NR_MIGRATE_BREAK;
goto redo; goto redo;
} }
goto out_all_pinned; goto out_all_pinned;

6
kernel/sched/sched.h
View File

@ -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); 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_nr_migrate;
extern const_debug unsigned int sysctl_sched_migration_cost; extern const_debug unsigned int sysctl_sched_migration_cost;