[PATCH 6/6] cgroup/cpuset: Iterate only if DEADLINE tasks are present

Juri Lelli
2023-03-29T12:55:58Z

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 <qyousef-wp2msK0BRk8tq7phqP6ubQ@public.gmane.org>
Link: https://lore.kernel.org/lkml/20230206221428.2125324-1-qyousef-wp2msK0BRk8tq7phqP6ubQ@public.gmane.org/
Signed-off-by: Juri Lelli <juri.lelli-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
kernel/cgroup/cpuset.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index f8ebec66da51..05c0a1255218 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1092,6 +1092,9 @@ static void dl_update_tasks_root_domain(struct cpuset *cs)
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)))
--
2.39.2