linux-kernel - Re: [PATCH] net-sysfs: Slightly optimize 'xps_queue

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Message-ID: <CADvbK_du8Oya986Ae9YJ+w5kkexE5S5mvAb+DWod-1_F85=sgA@mail.gmail.com>
Date:   Mon, 22 Nov 2021 10:23:05 -0500
From:   Xin Long <lucien.xin@...il.com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     davem <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
        atenart@...nel.org, Alexander Duyck <alexanderduyck@...com>,
        Paolo Abeni <pabeni@...hat.com>, Wei Wang <weiwan@...gle.com>,
        network dev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] net-sysfs: Slightly optimize 'xps_queue_show()'

On Sun, Nov 21, 2021 at 2:38 PM Christophe JAILLET
<christophe.jaillet@...adoo.fr> wrote:
>
> The 'mask' bitmap is local to this function. So the non-atomic
> '__set_bit()' can be used to save a few cycles.
>
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
>  net/core/net-sysfs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
> index 9c01c642cf9e..3be3f4a6add3 100644
> --- a/net/core/net-sysfs.c
> +++ b/net/core/net-sysfs.c
> @@ -1452,7 +1452,7 @@ static ssize_t xps_queue_show(struct net_device *dev, unsigned int index,
>
>                 for (i = map->len; i--;) {
>                         if (map->queues[i] == index) {
> -                               set_bit(j, mask);
> +                               __set_bit(j, mask);
>                                 break;
>                         }
>                 }
> --
> 2.30.2
>
The similar optimization can seem to be done in br_vlan.c and br_if.c as well.