[PATCH v7 5/5] cpuset: Make generate_sched_domains() recognize isolated_cpus

Waiman Long
2018-04-19T13:48:14Z

The generate_sched_domains() function and the hotplug code are modified
to make them use the newly introduced isolated_cpus mask for schedule
domains generation.

Signed-off-by: Waiman Long <longman@redhat.com>
---
kernel/cgroup/cpuset.c | 35 +++++++++++++++++++++++++++++++++--
1 file changed, 33 insertions(+), 2 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index d05c4c8..a67c77a 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -683,13 +683,14 @@ 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.isolation_count) {
ndoms = 1;
doms = alloc_sched_domains(ndoms);
if (!doms)
@@ -712,6 +713,8 @@ 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;
@@ -722,6 +725,9 @@ 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) &&
@@ -729,6 +735,10 @@ 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;

@@ -820,6 +830,12 @@ static int generate_sched_domains(cpumask_var_t **domains,
}
BUG_ON(nslot != ndoms);

+#ifdef CONFIG_DEBUG_KERNEL
+ for (i = 0; i < ndoms; i++)
+ pr_info("rebuild_sched_domains dom %d: %*pbl\n", i,
+ cpumask_pr_args(doms[i]));
+#endif
+
done:
kfree(csa);

@@ -860,7 +876,12 @@ 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.isolation_count &&
+ !cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
+ goto out;
+
+ if (top_cpuset.isolation_count &&
+ !cpumask_subset(top_cpuset.effective_cpus, cpu_active_mask))
goto out;

/* Generate domain masks and attrs */
@@ -1102,6 +1123,7 @@ static int update_isolated_cpumask(const char *buf)

top_cpuset.isolation_count = cpumask_weight(top_cpuset.isolated_cpus);
spin_unlock_irq(&callback_lock);
+ rebuild_sched_domains_locked();

out_ok:
retval = 0;
@@ -2530,6 +2552,11 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
cpumask_copy(&new_cpus, cpu_active_mask);
new_mems = node_states[N_MEMORY];

+ /*
+ * If isolated_cpus is populated, it is likely that the check below
+ * will produce a false positive on cpus_updated when the cpu list
+ * isn't changed. It is extra work, but it is better to be safe.
+ */
cpus_updated = !cpumask_equal(top_cpuset.effective_cpus, &new_cpus);
mems_updated = !nodes_equal(top_cpuset.effective_mems, new_mems);

@@ -2538,6 +2565,10 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
spin_lock_irq(&callback_lock);
if (!on_dfl)
cpumask_copy(top_cpuset.cpus_allowed, &new_cpus);
+
+ if (top_cpuset.isolation_count)
+ cpumask_andnot(&new_cpus, &new_cpus,
+ top_cpuset.isolated_cpus);
cpumask_copy(top_cpuset.effective_cpus, &new_cpus);
spin_unlock_irq(&callback_lock);
/* we don't mess with cpumasks of tasks in top_cpuset */
--
1.8.3.1