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Message-ID: <843bc3d3-5032-4913-84fb-dc2107f0b554@gmail.com>
Date: Wed, 24 Apr 2024 13:12:39 +0200
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Subject: Re: [PATCH-cgroup] cgroup/cpuset: Fix incorrect top_cpuset flags
To: Waiman Long <longman@redhat.com>, Tejun Heo <tj@kernel.org>,
 Zefan Li <lizefan.x@bytedance.com>, Johannes Weiner <hannes@cmpxchg.org>
Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
 Xiu Jianfeng <xiujianfeng@huawei.com>
References: <20240424010020.181305-1-longman@redhat.com>
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From: Klara Modin <klarasmodin@gmail.com>
In-Reply-To: <20240424010020.181305-1-longman@redhat.com>
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On 2024-04-24 03:00, Waiman Long wrote:
> Commit 8996f93fc388 ("cgroup/cpuset: Statically initialize more
> members of top_cpuset") uses an incorrect "<" relational operator for
> the CS_SCHED_LOAD_BALANCE bit when initializing the top_cpuset. This
> results in load_balancing turned off by default in the top cpuset which
> is bad for performance.
> 
> Fix this by using the BIT() helper macro to set the desired top_cpuset
> flags and avoid similar mistake from being made in the future.
> 
> Fixes: 8996f93fc388 ("cgroup/cpuset: Statically initialize more members of top_cpuset")
> Signed-off-by: Waiman Long <longman@redhat.com>
> ---
>   kernel/cgroup/cpuset.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index e70008a1d86a..b0a97efa5f20 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -368,8 +368,8 @@ static inline void notify_partition_change(struct cpuset *cs, int old_prs)
>   }
>   
>   static struct cpuset top_cpuset = {
> -	.flags = ((1 << CS_ONLINE) | (1 << CS_CPU_EXCLUSIVE) |
> -		  (1 << CS_MEM_EXCLUSIVE) | (1 < CS_SCHED_LOAD_BALANCE)),
> +	.flags = BIT(CS_ONLINE) | BIT(CS_CPU_EXCLUSIVE) |
> +		 BIT(CS_MEM_EXCLUSIVE) | BIT(CS_SCHED_LOAD_BALANCE),
>   	.partition_root_state = PRS_ROOT,
>   	.relax_domain_level = -1,
>   	.remote_sibling = LIST_HEAD_INIT(top_cpuset.remote_sibling),

I saw this made its way into today's next and can confirm it fixes the 
issue I reported in [1].

Thanks,
Tested-by: Klara Modin <klarasmodin@gmail.com>

1. 
https://lore.kernel.org/lkml/f2edf788-6ff3-43b1-9445-ac237e7910ac@gmail.com