linux-kernel - Re: [PATCH net-next v2 1/2] page_pool: use relaxed atomic for release side accounting

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Message-ID: <9363880e-4ed2-5acd-87da-d669b68d0134@redhat.com>
Date:   Fri, 20 Aug 2021 09:12:29 +0200
From:   Jesper Dangaard Brouer <jbrouer@...hat.com>
To:     Yunsheng Lin <linyunsheng@...wei.com>, davem@...emloft.net,
        kuba@...nel.org
Cc:     brouer@...hat.com, hawk@...nel.org, ilias.apalodimas@...aro.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        hkallweit1@...il.com
Subject: Re: [PATCH net-next v2 1/2] page_pool: use relaxed atomic for release
 side accounting


On 20/08/2021 08.56, Yunsheng Lin wrote:
> There is no need to synchronize the account updating, so
> use the relaxed atomic to avoid some memory barrier in the
> data path.
> 
> Signed-off-by: Yunsheng Lin <linyunsheng@...wei.com>

LGTM

Acked-by: Jesper Dangaard Brouer <brouer@...hat.com>

> ---
>   net/core/page_pool.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index e140905..1a69784 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -370,7 +370,7 @@ void page_pool_release_page(struct page_pool *pool, struct page *page)
>   	/* This may be the last page returned, releasing the pool, so
>   	 * it is not safe to reference pool afterwards.
>   	 */
> -	count = atomic_inc_return(&pool->pages_state_release_cnt);
> +	count = atomic_inc_return_relaxed(&pool->pages_state_release_cnt);
>   	trace_page_pool_state_release(pool, page, count);
>   }
>   EXPORT_SYMBOL(page_pool_release_page);
>