From: Waiman Long <longman@redhat.com> mainline inclusion from mainline-v6.11-rc1 commit 1805c1729f52edaa021288473b09f9c7f74fb1ca category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IAOPW2 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... ---------------------------------------------------------------------- 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@redhat.com> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Chen Ridong <chenridong@huawei.com> --- kernel/cgroup/cpuset.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index b681587b84ca..a5bbbfbb30a8 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1121,6 +1121,7 @@ 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) @@ -1179,6 +1180,13 @@ 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; -- 2.34.1