linux-kernel - Re: [PATCH -next] cgroup/cpuset: Avoid clearing CS_SCHED_LOAD

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Date: Mon, 22 Apr 2024 14:38:44 -0400
From: Waiman Long <longman@...hat.com>
To: Xiu Jianfeng <xiujianfeng@...wei.com>, lizefan.x@...edance.com,
 tj@...nel.org, hannes@...xchg.org
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] cgroup/cpuset: Avoid clearing CS_SCHED_LOAD_BALANCE
 twice

On 4/20/24 05:47, Xiu Jianfeng wrote:
> In cpuset_css_online(), CS_SCHED_LOAD_BALANCE has been cleared in the
> is_in_v2_mode() case under the same condition, don't do it twice.
>
> Signed-off-by: Xiu Jianfeng <xiujianfeng@...wei.com>
> ---
>   kernel/cgroup/cpuset.c | 7 -------
>   1 file changed, 7 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index e70008a1d86a..159525cdaeb9 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -4059,13 +4059,6 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
>   			clear_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
>   	}
>   
> -	/*
> -	 * For v2, clear CS_SCHED_LOAD_BALANCE if parent is isolated
> -	 */
> -	if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
> -	    !is_sched_load_balance(parent))
> -		clear_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
> -
>   	spin_unlock_irq(&callback_lock);
>   
>   	if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags))

Thanks for catching this duplication.

Could you remove the check inside is_in_v2_mode() instead? 
is_in_v2_mode() can be true for cgroup v1 if the"cpuset_v2_mode" mount 
option is specified. That balance flag change isn't appropriate for this 
particular case.

Thanks,
Longman