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Commit 8b5f1c52 authored by Li Zefan's avatar Li Zefan Committed by Tejun Heo
Browse files

cpuset: use effective cpumask to build sched domains 



We're going to have separate user-configured masks and effective ones.

Eventually configured masks can only be changed by writing cpuset.cpus
and cpuset.mems, and they won't be restricted by parent cpuset. While
effective masks reflect cpu/memory hotplug and hierachical restriction,
and these are the real masks that apply to the tasks in the cpuset.

We calculate effective mask this way:
  - top cpuset's effective_mask == online_mask, otherwise
  - cpuset's effective_mask == configured_mask & parent effective_mask,
    if the result is empty, it inherits parent effective mask.

Those behavior changes are for default hierarchy only. For legacy
hierarchy, effective_mask and configured_mask are the same, so we won't
break old interfaces.

We should partition sched domains according to effective_cpus, which
is the real cpulist that takes effects on tasks in the cpuset.

This won't introduce behavior change.

v2:
- Add a comment for the call of rebuild_sched_domains(), suggested
by Tejun.

Signed-off-by: default avatarLi Zefan <lizefan@huawei.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 554b0d1c

kernel/cpuset.c

+17 −11
Original line number Diff line number Diff line
@@ -494,11 +494,11 @@ static int validate_change(struct cpuset *cur, struct cpuset *trial) 
#ifdef CONFIG_SMP

/*

 * Helper routine for generate_sched_domains().

 * Do cpusets a, b have overlapping cpus_allowed masks?

 * Do cpusets a, b have overlapping effective cpus_allowed masks?

 */

static int cpusets_overlap(struct cpuset *a, struct cpuset *b)

{

	return cpumask_intersects(a->cpus_allowed, b->cpus_allowed);

	return cpumask_intersects(a->effective_cpus, b->effective_cpus);

}



static void
@@ -615,7 +615,7 @@ static int generate_sched_domains(cpumask_var_t **domains, 
			*dattr = SD_ATTR_INIT;

			update_domain_attr_tree(dattr, &top_cpuset);

		}

		cpumask_copy(doms[0], top_cpuset.cpus_allowed);

		cpumask_copy(doms[0], top_cpuset.effective_cpus);



		goto done;

	}
@@ -719,7 +719,7 @@ static int generate_sched_domains(cpumask_var_t **domains, 
			struct cpuset *b = csa[j];



			if (apn == b->pn) {

				cpumask_or(dp, dp, b->cpus_allowed);

				cpumask_or(dp, dp, b->effective_cpus);

				if (dattr)

					update_domain_attr_tree(dattr + nslot, b);
@@ -771,7 +771,7 @@ static void rebuild_sched_domains_locked(void) 
	 * passing doms with offlined cpu to partition_sched_domains().

	 * Anyways, hotplug work item will rebuild sched domains.

	 */

	if (!cpumask_equal(top_cpuset.cpus_allowed, cpu_active_mask))

	if (!cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))

		goto out;



	/* Generate domain masks and attrs */
@@ -870,6 +870,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct cpumask *new_cpus) 
{

	struct cpuset *cp;

	struct cgroup_subsys_state *pos_css;

	bool need_rebuild_sched_domains = false;



	rcu_read_lock();

	cpuset_for_each_descendant_pre(cp, pos_css, cs) {
@@ -903,10 +904,21 @@ static void update_cpumasks_hier(struct cpuset *cs, struct cpumask *new_cpus) 


		update_tasks_cpumask(cp);



		/*

		 * If the effective cpumask of any non-empty cpuset is changed,

		 * we need to rebuild sched domains.

		 */

		if (!cpumask_empty(cp->cpus_allowed) &&

		    is_sched_load_balance(cp))

			need_rebuild_sched_domains = true;



		rcu_read_lock();

		css_put(&cp->css);

	}

	rcu_read_unlock();



	if (need_rebuild_sched_domains)

		rebuild_sched_domains_locked();

}



/**
@@ -919,7 +931,6 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs, 
			  const char *buf)

{

	int retval;

	int is_load_balanced;



	/* top_cpuset.cpus_allowed tracks cpu_online_mask; it's read-only */

	if (cs == &top_cpuset)
@@ -950,17 +961,12 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs, 
	if (retval < 0)

		return retval;



	is_load_balanced = is_sched_load_balance(trialcs);



	mutex_lock(&callback_mutex);

	cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);

	mutex_unlock(&callback_mutex);



	/* use trialcs->cpus_allowed as a temp variable */

	update_cpumasks_hier(cs, trialcs->cpus_allowed);



	if (is_load_balanced)

		rebuild_sched_domains_locked();

	return 0;

}