From: "Michael S. Tsirkin" <mst@redhat•com>
To: Prashant Bhole <bhole_prashant_q7@lab•ntt.co.jp>
Cc: "David S . Miller" <davem@davemloft•net>,
Jason Wang <jasowang@redhat•com>,
netdev@vger•kernel.org,
Toshiaki Makita <makita.toshiaki@lab•ntt.co.jp>
Subject: Re: [PATCH net-next v2] tun: replace get_cpu_ptr with this_cpu_ptr when bh disabled
Date: Mon, 10 Dec 2018 22:31:06 -0500 [thread overview]
Message-ID: <20181210223057-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20181211024307.7156-1-bhole_prashant_q7@lab.ntt.co.jp>
On Tue, Dec 11, 2018 at 11:43:07AM +0900, Prashant Bhole wrote:
> tun_xdp_one() runs with local bh disabled. So there is no need to
> disable preemption by calling get_cpu_ptr while updating stats. This
> patch replaces the use of get_cpu_ptr() with this_cpu_ptr() as a
> micro-optimization. Also removes related put_cpu_ptr call.
>
> Acked-by: Jason Wang <jasowang@redhat•com>
> Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab•ntt.co.jp>
Acked-by: Michael S. Tsirkin <mst@redhat•com>
> ---
> v1 -> v2: Added comment to explain why this change is safe
>
> drivers/net/tun.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 6760b86547df..cb90859d0433 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -2494,12 +2494,14 @@ static int tun_xdp_one(struct tun_struct *tun,
> skb_record_rx_queue(skb, tfile->queue_index);
> netif_receive_skb(skb);
>
> - stats = get_cpu_ptr(tun->pcpu_stats);
> + /* No need for get_cpu_ptr() here since this function is
> + * always called with bh disabled
> + */
> + stats = this_cpu_ptr(tun->pcpu_stats);
> u64_stats_update_begin(&stats->syncp);
> stats->rx_packets++;
> stats->rx_bytes += skb->len;
> u64_stats_update_end(&stats->syncp);
> - put_cpu_ptr(stats);
>
> if (rxhash)
> tun_flow_update(tun, rxhash, tfile);
> --
> 2.17.2
>
next prev parent reply other threads:[~2018-12-11 3:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-11 2:43 [PATCH net-next v2] tun: replace get_cpu_ptr with this_cpu_ptr when bh disabled Prashant Bhole
2018-12-11 3:31 ` Michael S. Tsirkin [this message]
2018-12-14 21:33 ` David Miller
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20181210223057-mutt-send-email-mst@kernel.org \
--to=mst@redhat$(echo .)com \
--cc=bhole_prashant_q7@lab$(echo .)ntt.co.jp \
--cc=davem@davemloft$(echo .)net \
--cc=jasowang@redhat$(echo .)com \
--cc=makita.toshiaki@lab$(echo .)ntt.co.jp \
--cc=netdev@vger$(echo .)kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox