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Subject[PATCH v14 08/12] cpuset: Make generate_sched_domains() work with partition
Date
The generate_sched_domains() function is modified to make it work
correctly with the newly introduced subparts_cpus mask for scheduling
domains generation.

Signed-off-by: Waiman Long <longman@redhat.com>
---
kernel/cgroup/cpuset.c | 34 +++++++++++++++++++++++++++-------
1 file changed, 27 insertions(+), 7 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 2e9fab21ea57..53dbd473bd7e 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -769,13 +769,14 @@ static int generate_sched_domains(cpumask_var_t **domains,
int ndoms = 0; /* number of sched domains in result */
int nslot; /* next empty doms[] struct cpumask slot */
struct cgroup_subsys_state *pos_css;
+ bool root_load_balance = is_sched_load_balance(&top_cpuset);

doms = NULL;
dattr = NULL;
csa = NULL;

/* Special case for the 99% of systems with one, full, sched domain */
- if (is_sched_load_balance(&top_cpuset)) {
+ if (root_load_balance && !top_cpuset.nr_subparts_cpus) {
ndoms = 1;
doms = alloc_sched_domains(ndoms);
if (!doms)
@@ -798,6 +799,8 @@ static int generate_sched_domains(cpumask_var_t **domains,
csn = 0;

rcu_read_lock();
+ if (root_load_balance)
+ csa[csn++] = &top_cpuset;
cpuset_for_each_descendant_pre(cp, pos_css, &top_cpuset) {
if (cp == &top_cpuset)
continue;
@@ -808,6 +811,9 @@ static int generate_sched_domains(cpumask_var_t **domains,
* parent's cpus, so just skip them, and then we call
* update_domain_attr_tree() to calc relax_domain_level of
* the corresponding sched domain.
+ *
+ * If root is load-balancing, we can skip @cp if it
+ * is a subset of the root's effective_cpus.
*/
if (!cpumask_empty(cp->cpus_allowed) &&
!(is_sched_load_balance(cp) &&
@@ -815,11 +821,16 @@ static int generate_sched_domains(cpumask_var_t **domains,
housekeeping_cpumask(HK_FLAG_DOMAIN))))
continue;

+ if (root_load_balance &&
+ cpumask_subset(cp->cpus_allowed, top_cpuset.effective_cpus))
+ continue;
+
if (is_sched_load_balance(cp))
csa[csn++] = cp;

- /* skip @cp's subtree */
- pos_css = css_rightmost_descendant(pos_css);
+ /* skip @cp's subtree if not a partition root */
+ if (!is_partition_root(cp))
+ pos_css = css_rightmost_descendant(pos_css);
}
rcu_read_unlock();

@@ -947,7 +958,12 @@ 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.effective_cpus, cpu_active_mask))
+ if (!top_cpuset.nr_subparts_cpus &&
+ !cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
+ goto out;
+
+ if (top_cpuset.nr_subparts_cpus &&
+ !cpumask_subset(top_cpuset.effective_cpus, cpu_active_mask))
goto out;

/* Generate domain masks and attrs */
@@ -1362,11 +1378,15 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
update_tasks_cpumask(cp);

/*
- * If the effective cpumask of any non-empty cpuset is changed,
- * we need to rebuild sched domains.
+ * On legacy hierarchy, if the effective cpumask of any non-
+ * empty cpuset is changed, we need to rebuild sched domains.
+ * On default hierarchy, the cpuset needs to be a partition
+ * root as well.
*/
if (!cpumask_empty(cp->cpus_allowed) &&
- is_sched_load_balance(cp))
+ is_sched_load_balance(cp) &&
+ (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||
+ is_partition_root(cp)))
need_rebuild_sched_domains = true;

rcu_read_lock();
--
2.18.0
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