This is a note to let you know that I've just added the patch titled
cgroup/cpuset: Iterate only if DEADLINE tasks are present
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
cgroup-cpuset-iterate-only-if-deadline-tasks-are-present.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From stable-owner@xxxxxxxxxxxxxxx Sun Aug 20 17:26:08 2023
From: Qais Yousef <qyousef@xxxxxxxxxxx>
Date: Sun, 20 Aug 2023 16:22:56 +0100
Subject: cgroup/cpuset: Iterate only if DEADLINE tasks are present
To: stable@xxxxxxxxxxxxxxx
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>, Waiman Long <longman@xxxxxxxxxx>, Tejun Heo <tj@xxxxxxxxxx>, Dietmar Eggemann <dietmar.eggemann@xxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Vincent Guittot <vincent.guittot@xxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Hao Luo <haoluo@xxxxxxxxxx>, John Stultz <jstultz@xxxxxxxxxx>, cgroups@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Qais Yousef <qyousef@xxxxxxxxxxx>
Message-ID: <20230820152258.518128-5-qyousef@xxxxxxxxxxx>
From: Juri Lelli <juri.lelli@xxxxxxxxxx>
commit c0f78fd5edcf29b2822ac165f9248a6c165e8554 upstream.
update_tasks_root_domain currently iterates over all tasks even if no
DEADLINE task is present on the cpuset/root domain for which bandwidth
accounting is being rebuilt. This has been reported to introduce 10+ ms
delays on suspend-resume operations.
Skip the costly iteration for cpusets that don't contain DEADLINE tasks.
Reported-by: Qais Yousef (Google) <qyousef@xxxxxxxxxxx>
Link: https://lore.kernel.org/lkml/20230206221428.2125324-1-qyousef@xxxxxxxxxxx/
Signed-off-by: Juri Lelli <juri.lelli@xxxxxxxxxx>
Reviewed-by: Waiman Long <longman@xxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Qais Yousef (Google) <qyousef@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/cgroup/cpuset.c | 3 +++
1 file changed, 3 insertions(+)
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -966,6 +966,9 @@ static void dl_update_tasks_root_domain(
struct css_task_iter it;
struct task_struct *task;
+ if (cs->nr_deadline_tasks == 0)
+ return;
+
css_task_iter_start(&cs->css, 0, &it);
while ((task = css_task_iter_next(&it)))
Patches currently in stable-queue which might be from stable-owner@xxxxxxxxxxxxxxx are
queue-5.15/cgroup-cpuset-free-dl-bw-in-case-can_attach-fails.patch
queue-5.15/sched-cpuset-keep-track-of-sched_deadline-task-in-cpusets.patch
queue-5.15/cgroup-cpuset-rename-functions-dealing-with-deadline-accounting.patch
queue-5.15/cgroup-cpuset-iterate-only-if-deadline-tasks-are-present.patch
queue-5.15/sched-cpuset-bring-back-cpuset_mutex.patch
queue-5.15/sched-deadline-create-dl-bw-alloc-free-check-overflow-interface.patch
