linux-kernel - Re: [PATCH] mm: page_alloc: Remove redundant READ

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Message-ID: <ade19125-c9da-47dc-aab5-4d83b799e54d@bytedance.com>
Date: Wed, 2 Apr 2025 15:59:51 +0800
From: Qi Zheng <zhengqi.arch@...edance.com>
To: Songtang Liu <liusongtang@...edance.com>, akpm@...ux-foundation.org,
 ying.huang@...ux.alibaba.com
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 zhengqi.arch@...edance.com, songmuchun@...edance.com
Subject: Re: [PATCH] mm: page_alloc: Remove redundant READ_ONCE



On 4/2/25 3:41 PM, Songtang Liu wrote:
> In the current code, batch is a local variable, and it cannot be
> concurrently modified. It's unnecessary to use READ_ONCE here,
> so remove it.
> 
> Fixes: 51a755c56dc0 ("mm: tune PCP high automatically")
> Signed-off-by: Songtang Liu <liusongtang@...edance.com>
> ---
>   mm/page_alloc.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index e3ea5bf5c459..6edc6e57d4f8 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2661,7 +2661,7 @@ static void free_frozen_page_commit(struct zone *zone,
>   		free_high = (pcp->free_count >= batch &&
>   			     (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) &&
>   			     (!(pcp->flags & PCPF_FREE_HIGH_BATCH) ||
> -			      pcp->count >= READ_ONCE(batch)));
> +			      pcp->count >= batch));
>   		pcp->flags |= PCPF_PREV_FREE_HIGH_ORDER;
>   	} else if (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) {
>   		pcp->flags &= ~PCPF_PREV_FREE_HIGH_ORDER;

Reviewed-by: Qi Zheng <zhengqi.arch@...edance.com>

Thanks!