From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: Re: [PATCH v9 3/8] cpuset: Rebuild root domain deadline accounting information Date: Fri, 16 Dec 2022 21:26:20 -0500 Message-ID: References: <20190719140000.31694-1-juri.lelli@redhat.com> <20190719140000.31694-4-juri.lelli@redhat.com> <20221216233501.gh6m75e7s66dmjgo@airbuntu> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1671243985; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Ji+gytidbXOMWyPvLX4LLTm6QX/OlsVTfQzF/90xBXs=; b=MXI2utrq6URdh6bfTl9jqQNgccUlFLaPsw157Cflrqr3gTb4XGWRx2mzTVVjYbCXcZc9Ug 6Z3ltm26By35qYCFACxEKzr2/ZNxGHvmBvJr7dWLqnDyfjHH+9cCL51SUZiwuhGTBEJj0a KzO3urTPvxj9o244UXmXMTI3+Oi9GdE= Content-Language: en-US In-Reply-To: <20221216233501.gh6m75e7s66dmjgo@airbuntu> List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Qais Yousef , Juri Lelli Cc: 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 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. Cheers, Longman