linux-kernel - Re: [PATCH] mm: memcontrol: eliminate redundant check in __mem_cgroup_insert

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Message-ID: <20201009151227.GP4967@dhcp22.suse.cz>
Date:   Fri, 9 Oct 2020 17:12:27 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     akpm@...ux-foundation.org, hannes@...xchg.org,
        vdavydov.dev@...il.com, cgroups@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: memcontrol: eliminate redundant check in
 __mem_cgroup_insert_exceeded()

On Fri 09-10-20 09:51:04, Miaohe Lin wrote:
> The mz->usage_in_excess >= mz_node->usage_in_excess check is exactly the
> else case of mz->usage_in_excess < mz_node->usage_in_excess. So we could
> replace else if (mz->usage_in_excess >= mz_node->usage_in_excess) with else
> equally.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>

Acked-by: Michal Hocko <mhocko@...e.com>

I believe this is a result of a very unreadable code. Resp. the comment
makes it hard to follow. It would be slightly better to simply drop the
comment which doesn't really explain much IMHO.

> ---
>  mm/memcontrol.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 2636f8bad908..f607afd0fcbf 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -629,7 +629,7 @@ static void __mem_cgroup_insert_exceeded(struct mem_cgroup_per_node *mz,
>  		 * We can't avoid mem cgroups that are over their soft
>  		 * limit by the same amount
>  		 */
> -		else if (mz->usage_in_excess >= mz_node->usage_in_excess)
> +		else
>  			p = &(*p)->rb_right;
>  	}
>  
> -- 
> 2.19.1

-- 
Michal Hocko
SUSE Labs