netdev - Re: [PATCH net-next v3] page_pool: use relaxed atomic for release side accounting

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Message-ID: <CAC_iWj+UefbRUdd9m_Mb6G=KvEV0TpTH9SAN1PSYAvQObL6ZRA@mail.gmail.com>
Date:   Tue, 24 Aug 2021 12:12:17 +0300
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     Yunsheng Lin <linyunsheng@...wei.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Networking <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: [PATCH net-next v3] page_pool: use relaxed atomic for release
 side accounting

On Tue, 24 Aug 2021 at 12:07, Yunsheng Lin <linyunsheng@...wei.com> wrote:
>
> There is no need to synchronize the account updating, so
> use the relaxed atomic to avoid some memory barrier in the
> data path.
>
> Acked-by: Jesper Dangaard Brouer <brouer@...hat.com>
> Signed-off-by: Yunsheng Lin <linyunsheng@...wei.com>
> ---
> V3: Drop patch 2.
> V2: Remove unnecessary unliky() mark as pointed out by
>     Heiner.
> ---
>  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);
> --
> 2.7.4
>