From c9546921a4b97813254c74ba3d1870f53f02e2ad Mon Sep 17 00:00:00 2001 From: Juri Lelli Date: Sun, 20 Aug 2023 16:21:42 +0100 Subject: [PATCH] cgroup/cpuset: Iterate only if DEADLINE tasks are present 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) Link: https://lore.kernel.org/lkml/20230206221428.2125324-1-qyousef@layalina.io/ Signed-off-by: Juri Lelli Reviewed-by: Waiman Long Signed-off-by: Tejun Heo Signed-off-by: Qais Yousef (Google) Signed-off-by: Greg Kroah-Hartman --- kernel/cgroup/cpuset.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index fa8684c790a9..6c69e715b05a 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -937,6 +937,9 @@ 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)))