Re: [PATCH v2 4/6] cgroup/cpuset: Iterate only if DEADLINE tasks are present

Waiman Long
2023-05-03T17:57:31Z

On 5/3/23 03:22, Juri Lelli wrote:
> 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@layalina.io>
> Link: https://lore.kernel.org/lkml/20230206221428.2125324-1-qyousef@layalina.io/
> Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
> ---
> kernel/cgroup/cpuset.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index b9f4d5602517..6587df42cb61 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -1090,6 +1090,9 @@ 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)))
Reviewed-by: Waiman Long <longman@redhat.com>