Messages in this thread | | | Date | Fri, 20 Jan 2023 17:16:55 -0500 | Subject | Re: [PATCH v2] sched: cpuset: Don't rebuild sched domains on suspend-resume | From | Waiman Long <> |
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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@google.com> > Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io> > --- > > 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
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