From 1805c1729f52edaa021288473b09f9c7f74fb1ca Mon Sep 17 00:00:00 2001 From: Waiman Long Date: Mon, 3 Jun 2024 15:38:22 -0400 Subject: [PATCH] cgroup/cpuset: Optimize isolated partition only generate_sched_domains() calls 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 Signed-off-by: Tejun Heo --- kernel/cgroup/cpuset.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 315f8cbd6d35..f9b97f65e204 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;