From mboxrd@z Thu Jan 1 00:00:00 1970 From: Qais Yousef Subject: Re: [PATCH v9 3/8] cpuset: Rebuild root domain deadline accounting information Date: Sat, 17 Dec 2022 22:10:11 +0000 Message-ID: <20221217221011.pqunktdfgkaoufrd@airbuntu> References: <20190719140000.31694-1-juri.lelli@redhat.com> <20190719140000.31694-4-juri.lelli@redhat.com> <20221216233501.gh6m75e7s66dmjgo@airbuntu> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=layalina-io.20210112.gappssmtp.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=KgznWvPnejDwQ5G194p3C76c3g3BZCk+ljWB2J8CwsQ=; b=z60Sqh8HjXVzJehaGoNvHfThICmNQU5lyWECyXUwoLZzKHyW9IHSXNmSWfyibVk0qW sLCWrbAdZFv6iyQBOPoWofv3FHef9K4l2JVI3ilXVkmp5ccAWbk07qMJTtcBt33VvGt6 w61fp0MZNGXsFgXU9m9Uw+w0IsRqbnGCDFzMh5PEiav/r5b/Y5eJxOBH2qVNIOIP9RXv /WOsw+fuuy0EViw1TBP9jTZXo8bFfl2dWhIoXkQlCE2V9ULtRLS1vqMxUpV+/WuBNhVY vkwYXE8cUzsNbKOqkn+wgFEixC0PPzcsIl2XmdOoES8b7dJ3OUn14AomYEJA4XwRi2bC zNRg== Content-Disposition: inline In-Reply-To: List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Waiman Long Cc: Juri Lelli , peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org, tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, luca.abeni-5rdYK369eBLQB0XuIGIEkQ@public.gmane.org, claudio-YOzL5CV4y4YG1A2ADO40+w@public.gmane.org, tommaso.cucinotta-5rdYK369eBLQB0XuIGIEkQ@public.gmane.org, bristot-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, mathieu.poirier-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, dietmar.eggemann-5wv7dgnIgG8@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Vincent Guittot , Wei Wang , Rick Yiu , Quentin Perret 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 > > > Signed-off-by: Juri Lelli > > > --- > > 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 > > 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 > > Signed-off-by: Qais Yousef (Google) > > --- > > 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!