Commit 3ae0b773 authored by Waiman Long's avatar Waiman Long Committed by Tejun Heo
Browse files

cgroup/cpuset: Allow suppression of sched domain rebuild in update_cpumasks_hier() 



A single partition setup and tear-down operation can lead to
multiple rebuild_sched_domains_locked() calls which is a waste of
effort. This can partly be mitigated by adding a flag to suppress the
rebuild_sched_domains_locked() call in update_cpumasks_hier(). Since
a Boolean flag has already been passed as the 3rd argument to
update_cpumasks_hier(), we can extend that to a full flag word.

The sched domain rebuild suppression is now enabled in
update_sibling_cpumasks() as all it callers will do the sched domain
rebuild after its return later on anyway.

Signed-off-by: default avatarWaiman Long <longman@redhat.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 99fe36ba

kernel/cgroup/cpuset.c

+16 −8
Original line number Diff line number Diff line
@@ -1590,6 +1590,12 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd, 
	return 0;

}



/*

 * update_cpumasks_hier() flags

 */

#define HIER_CHECKALL		0x01	/* Check all cpusets with no skipping */

#define HIER_NO_SD_REBUILD	0x02	/* Don't rebuild sched domains */



/*

 * update_cpumasks_hier - Update effective cpumasks and tasks in the subtree

 * @cs:  the cpuset to consider
@@ -1604,7 +1610,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd, 
 * Called with cpuset_mutex held

 */

static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp,

				 bool force)

				 int flags)

{

	struct cpuset *cp;

	struct cgroup_subsys_state *pos_css;
@@ -1644,10 +1650,10 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp, 
		 * Skip the whole subtree if

		 * 1) the cpumask remains the same,

		 * 2) has no partition root state,

		 * 3) force flag not set, and

		 * 3) HIER_CHECKALL flag not set, and

		 * 4) for v2 load balance state same as its parent.

		 */

		if (!cp->partition_root_state && !force &&

		if (!cp->partition_root_state && !(flags & HIER_CHECKALL) &&

		    cpumask_equal(tmp->new_cpus, cp->effective_cpus) &&

		    (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||

		    (is_sched_load_balance(parent) == is_sched_load_balance(cp)))) {
@@ -1764,7 +1770,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp, 
	}

	rcu_read_unlock();



	if (need_rebuild_sched_domains)

	if (need_rebuild_sched_domains && !(flags & HIER_NO_SD_REBUILD))

		rebuild_sched_domains_locked();

}
@@ -1788,7 +1794,9 @@ static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs, 
	 * to use the right effective_cpus value.

	 *

	 * The update_cpumasks_hier() function may sleep. So we have to

	 * release the RCU read lock before calling it.

	 * release the RCU read lock before calling it. HIER_NO_SD_REBUILD

	 * flag is used to suppress rebuild of sched domains as the callers

	 * will take care of that.

	 */

	rcu_read_lock();

	cpuset_for_each_child(sibling, pos_css, parent) {
@@ -1800,7 +1808,7 @@ static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs, 
			continue;



		rcu_read_unlock();

		update_cpumasks_hier(sibling, tmp, false);

		update_cpumasks_hier(sibling, tmp, HIER_NO_SD_REBUILD);

		rcu_read_lock();

		css_put(&sibling->css);

	}
@@ -1913,7 +1921,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs, 
	spin_unlock_irq(&callback_lock);



	/* effective_cpus will be updated here */

	update_cpumasks_hier(cs, &tmp, false);

	update_cpumasks_hier(cs, &tmp, 0);



	if (cs->partition_root_state) {

		struct cpuset *parent = parent_cs(cs);
@@ -2382,7 +2390,7 @@ static int update_prstate(struct cpuset *cs, int new_prs) 
	 * Force update if switching back to member.

	 */

	if (!list_empty(&cs->css.children))

		update_cpumasks_hier(cs, &tmpmask, !new_prs);

		update_cpumasks_hier(cs, &tmpmask, !new_prs ? HIER_CHECKALL : 0);



	/* Update sched domains and load balance flag */

	update_partition_sd_lb(cs, old_prs);