On 1/20/23 14:48, Qais Yousef wrote:
Commit f9a25f776d78 ("cpusets: Rebuild root domain deadline accounting information")
enabled rebuilding sched domain on cpuset and hotplug operations to
correct deadline accounting.
Rebuilding sched domain is a slow operation and we see 10+ ms delay on
suspend-resume because of that.
Since nothing is expected to change on suspend-resume operation; skip
rebuilding the sched domains to regain the time lost.
Debugged-by: Rick Yiu <rickyiu@xxxxxxxxxx>
Signed-off-by: Qais Yousef (Google) <qyousef@xxxxxxxxxxx>
---
Changes in v2:
* Remove redundant check in update_tasks_root_domain() (Thanks Waiman)
v1 link:
https://lore.kernel.org/lkml/20221216233501.gh6m75e7s66dmjgo@airbuntu/
kernel/cgroup/cpuset.c | 3 +++
kernel/sched/deadline.c | 3 +++
2 files changed, 6 insertions(+)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index a29c0b13706b..9a45f083459c 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1088,6 +1088,9 @@ static void rebuild_root_domains(void)
lockdep_assert_cpus_held();
lockdep_assert_held(&sched_domains_mutex);
+ if (cpuhp_tasks_frozen)
+ return;
+
rcu_read_lock();
/*
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 0d97d54276cc..42c1143a3956 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -2575,6 +2575,9 @@ void dl_clear_root_domain(struct root_domain *rd)
{
unsigned long flags;
+ if (cpuhp_tasks_frozen)
+ return;
+
raw_spin_lock_irqsave(&rd->dl_bw.lock, flags);
rd->dl_bw.total_bw = 0;
raw_spin_unlock_irqrestore(&rd->dl_bw.lock, flags);
cpuhp_tasks_frozen is set when thaw_secondary_cpus() or
freeze_secondary_cpus() is called. I don't know the exact suspend/resume
calling sequences, will cpuhp_tasks_frozen be cleared at the end of
resume sequence? Maybe we should make sure that rebuild_root_domain() is
called at least once at the end of resume operation.
Cheers,
Longman
