Messages in this thread | | | Date | Fri, 16 Dec 2022 21:26:20 -0500 | Subject | Re: [PATCH v9 3/8] cpuset: Rebuild root domain deadline accounting information | From | Waiman Long <> |
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On 12/16/22 18:35, Qais Yousef wrote: > Hi > > On 07/19/19 15:59, Juri Lelli wrote: >> When the topology of root domains is modified by CPUset or CPUhotplug >> operations information about the current deadline bandwidth held in the >> root domain is lost. >> >> This patch addresses the issue by recalculating the lost deadline >> bandwidth information by circling through the deadline tasks held in >> CPUsets and adding their current load to the root domain they are >> associated with. >> >> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org> >> Signed-off-by: Juri Lelli <juri.lelli@redhat.com> >> --- > We see that rebuild_root_domain() can take 10+ ms (I get a max of 20ms quite > consistently) on suspend/resume. > > Do we actually need to rebuild_root_domain() if we're going through > a suspend/resume cycle? > > ie: would something like the below make sense? We'd skip this logic if > cpuhp_tasks_frozen is set which indicates it's not a real hotplug operation but > we're suspending/resuming. > > > Cheers > > -- > Qais Yousef > > > --->8--- > > > From 4cfd50960ad872c5eb810ad3038eaf840bab5182 Mon Sep 17 00:00:00 2001 > From: Qais Yousef <qyousef@layalina.io> > Date: Tue, 29 Nov 2022 19:01:52 +0000 > Subject: [PATCH] sched: cpuset: Don't rebuild sched domains on suspend-resume > > 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 delays > on suspend-resume because of that. > > Since nothing is expected to change on suspend-resume operation; skip > rebuilding the sched domains to regain some of the time lost. > > Debugged-by: Rick Yiu <rickyiu@google.com> > Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io> > --- > kernel/cgroup/cpuset.c | 6 ++++++ > kernel/sched/deadline.c | 3 +++ > 2 files changed, 9 insertions(+) > > diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c > index b474289c15b8..2ff68d625b7b 100644 > --- a/kernel/cgroup/cpuset.c > +++ b/kernel/cgroup/cpuset.c > @@ -1067,6 +1067,9 @@ static void update_tasks_root_domain(struct cpuset *cs) > struct css_task_iter it; > struct task_struct *task; > > + if (cpuhp_tasks_frozen) > + return; > + > css_task_iter_start(&cs->css, 0, &it); > > while ((task = css_task_iter_next(&it))) > @@ -1084,6 +1087,9 @@ static void rebuild_root_domains(void) > lockdep_assert_cpus_held(); > lockdep_assert_held(&sched_domains_mutex); > > + if (cpuhp_tasks_frozen) > + return; > + > rcu_read_lock(); > > /*
rebuild_root_domains() is the only caller of update_tasks_root_domain(). So the first hunk is redundant as update_tasks_root_domain() won't be called when cpuhp_tasks_frozen is set.
Cheers, Longman
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