sched/debug: Dump domains' level

Knowing domain's level exactly can be useful when setting
relax_domain_level or cpuset.sched_relax_domain_level

Usage:

  cat /debug/sched/domains/cpu0/domain1/level

to dump cpu0 domain1's level.

SDM macro is not used because sd->level is 'int' and
it would hide the type mismatch between 'int' and 'u32'.

Signed-off-by: Vitalii Bursov <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Tested-by: Dietmar Eggemann <[email protected]>
Acked-by: Vincent Guittot <[email protected]>
Reviewed-by: Valentin Schneider <[email protected]>
Link: https://lore.kernel.org/r/9489b6475f6dd6fbc67c617752d4216fa094da53.1714488502.git.vitaly@bursov.com

Author: vitalyvb

kernel/sched/debug.c

@@ -425,6 +425,7 @@ static void register_sd(struct sched_domain *sd, struct dentry *parent)
 
 	debugfs_create_file("flags", 0444, parent, &sd->flags, &sd_flags_fops);
 	debugfs_create_file("groups_flags", 0444, parent, &sd->groups->flags, &sd_flags_fops);
+	debugfs_create_u32("level", 0444, parent, (u32 *)&sd->level);
 }
 
 void update_sched_domain_debugfs(void)