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@xxxxxxxxxx>
Signed-off-by: Juri Lelli <juri.lelli@xxxxxxxxxx>
---
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@xxxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Qais Yousef (Google) <qyousef@xxxxxxxxxxx>
---
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
