From: Qais Yousef <qyousef@layalina.io>
To: Waiman Long <longman@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>,
peterz@infradead.org, mingo@redhat.com, rostedt@goodmis.org,
tj@kernel.org, linux-kernel@vger.kernel.org,
luca.abeni@santannapisa.it, claudio@evidence.eu.com,
tommaso.cucinotta@santannapisa.it, bristot@redhat.com,
mathieu.poirier@linaro.org, lizefan@huawei.com,
dietmar.eggemann@arm.com, cgroups@vger.kernel.org,
Vincent Guittot <vincent.guittot@linaro.org>,
Wei Wang <wvw@google.com>, Rick Yiu <rickyiu@google.com>,
Quentin Perret <qperret@google.com>
Subject: Re: [PATCH v9 3/8] cpuset: Rebuild root domain deadline accounting information
Date: Sat, 17 Dec 2022 22:10:11 +0000 [thread overview]
Message-ID: <20221217221011.pqunktdfgkaoufrd@airbuntu> (raw)
In-Reply-To: <af29b121-b1da-64f3-a739-1b233fa04002@redhat.com>
On 12/16/22 21:26, Waiman Long wrote:
> 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.
True. I went overzealous and protected all the functions.
Thanks!
--
Qais Yousef
next prev parent reply other threads:[~2022-12-17 22:10 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-19 13:59 [PATCH v9 0/8] sched/deadline: fix cpusets bandwidth accounting Juri Lelli
2019-07-19 13:59 ` [PATCH v9 1/8] sched/topology: Adding function partition_sched_domains_locked() Juri Lelli
2019-07-25 16:19 ` [tip:sched/core] sched/topology: Add partition_sched_domains_locked() tip-bot for Mathieu Poirier
2019-07-19 13:59 ` [PATCH v9 2/8] sched/core: Streamlining calls to task_rq_unlock() Juri Lelli
2019-07-22 8:21 ` Dietmar Eggemann
2019-07-22 8:32 ` Juri Lelli
2019-07-22 9:08 ` Dietmar Eggemann
2019-07-23 10:32 ` Peter Zijlstra
2019-07-23 10:31 ` Peter Zijlstra
2019-07-23 13:11 ` Tejun Heo
2019-07-23 14:58 ` Juri Lelli
2019-07-25 16:20 ` [tip:sched/core] sched/core: Streamle " tip-bot for Mathieu Poirier
2019-07-19 13:59 ` [PATCH v9 3/8] cpuset: Rebuild root domain deadline accounting information Juri Lelli
2019-07-25 13:53 ` Ingo Molnar
2019-07-25 13:56 ` Ingo Molnar
2019-07-25 14:07 ` Juri Lelli
2019-07-25 16:00 ` Mathieu Poirier
2019-07-25 16:21 ` [tip:sched/core] cpusets: " tip-bot for Mathieu Poirier
2019-11-04 18:57 ` [PATCH v9 3/8] cpuset: " Michal Koutný
2019-11-05 12:03 ` Michal Koutný
2022-12-16 23:35 ` Qais Yousef
2022-12-17 2:26 ` Waiman Long
2022-12-17 22:10 ` Qais Yousef [this message]
2022-12-19 8:07 ` Vincent Guittot
2022-12-20 11:43 ` Qais Yousef
2023-01-15 16:41 ` Qais Yousef
2019-07-19 13:59 ` [PATCH v9 4/8] sched/deadline: Fix bandwidth accounting at all levels after offline migration Juri Lelli
2019-07-22 11:07 ` Dietmar Eggemann
2019-07-22 12:28 ` Juri Lelli
2019-07-22 13:21 ` Dietmar Eggemann
2019-07-22 13:35 ` Juri Lelli
2019-07-22 14:29 ` Dietmar Eggemann
2019-07-25 16:21 ` [tip:sched/core] " tip-bot for Juri Lelli
2019-07-19 13:59 ` [PATCH v9 5/8] cgroup/cpuset: convert cpuset_mutex to percpu_rwsem Juri Lelli
2019-07-25 16:22 ` [tip:sched/core] cgroup/cpuset: Convert " tip-bot for Juri Lelli
2019-07-19 13:59 ` [PATCH v9 6/8] cgroup/cpuset: Change cpuset_rwsem and hotplug lock order Juri Lelli
2019-07-25 16:23 ` [tip:sched/core] " tip-bot for Juri Lelli
2019-07-19 13:59 ` [PATCH v9 7/8] rcu/tree: Setschedule gp ktread to SCHED_FIFO outside of atomic region Juri Lelli
2019-07-25 16:24 ` [tip:sched/core] rcu/tree: Call setschedule() " tip-bot for Juri Lelli
2019-07-19 14:00 ` [PATCH v9 8/8] sched/core: Prevent race condition between cpuset and __sched_setscheduler() Juri Lelli
2019-07-25 16:24 ` [tip:sched/core] " tip-bot for Juri Lelli
2019-07-24 8:45 ` [PATCH v9 0/8] sched/deadline: fix cpusets bandwidth accounting Dietmar Eggemann
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