6.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Waiman Long <longman@xxxxxxxxxx>
[ Upstream commit 1805c1729f52edaa021288473b09f9c7f74fb1ca ]
If only isolated partitions are being created underneath the cgroup root,
there will only be one sched domain with top_cpuset.effective_cpus. We can
skip the unnecessary sched domains scanning code and save some cycles.
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Stable-dep-of: ccac8e8de99c ("cgroup/cpuset: Fix remote root partition creation problem")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
kernel/cgroup/cpuset.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index c12b9fdb22a4e..73ab45b04c000 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -964,6 +964,7 @@ static int generate_sched_domains(cpumask_var_t **domains,
/* Special case for the 99% of systems with one, full, sched domain */
if (root_load_balance && !top_cpuset.nr_subparts) {
+single_root_domain:
ndoms = 1;
doms = alloc_sched_domains(ndoms);
if (!doms)
@@ -1022,6 +1023,13 @@ static int generate_sched_domains(cpumask_var_t **domains,
}
rcu_read_unlock();
+ /*
+ * If there are only isolated partitions underneath the cgroup root,
+ * we can optimize out unneeded sched domains scanning.
+ */
+ if (root_load_balance && (csn == 1))
+ goto single_root_domain;
+
for (i = 0; i < csn; i++)
csa[i]->pn = i;
ndoms = csn;
--
2.43.0
