From: Juri Lelli Date: Mon, 21 Aug 2023 22:19:54 +0000 (+0100) Subject: cgroup/cpuset: Iterate only if DEADLINE tasks are present X-Git-Tag: v6.4.13~48 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c95a751498c9f3cc7c6f94b14da196bd38610d9c;p=thirdparty%2Fkernel%2Fstable.git 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 --- diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index ca195ff8b298b..b7168970fff2e 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)))