From: Pavel Begunkov <asml.silence@gmail.com>
To: David Ahern <dsahern@gmail.com>,
io-uring@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: Jakub Kicinski <kuba@kernel.org>,
Jonathan Lemon <jonathan.lemon@gmail.com>,
"David S . Miller" <davem@davemloft.net>,
Willem de Bruijn <willemb@google.com>,
Eric Dumazet <edumazet@google.com>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
David Ahern <dsahern@kernel.org>, Jens Axboe <axboe@kernel.dk>
Subject: Re: [RFC 00/12] io_uring zerocopy send
Date: Wed, 1 Dec 2021 20:15:28 +0000 [thread overview]
Message-ID: <974b266e-d224-97da-708f-c4a7e7050190@gmail.com> (raw)
In-Reply-To: <0b92f046-5ac3-7138-2775-59fadee6e17a@gmail.com>
On 12/1/21 19:20, David Ahern wrote:
> On 12/1/21 12:11 PM, Pavel Begunkov wrote:
>> btw, why a dummy device would ever go through loopback? It doesn't
>> seem to make sense, though may be missing something.
>
> You are sending to a local ip address, so the fib_lookup returns
> RTN_LOCAL. The code makes dev_out the loopback:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/tree/net/ipv4/route.c#n2773
I see, thanks. I still don't use the skb_orphan_frags_rx() hack
and it doesn't go through the loopback (for my dummy tests), just
dummy_xmit() and no mention of loopback in perf data, see the
flamegraph. Don't know what is the catch.
I'm illiterate of the routing paths. Can it be related to
the "ip route add"? How do you get an ipv4 address for the device?
>
> (you are not using vrf so ignore the l3mdev reference). loopback device
> has the logic to put the skb back in the stack for Rx processing:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/tree/drivers/net/loopback.c#n68
>
--
Pavel Begunkov
next prev parent reply other threads:[~2021-12-01 20:17 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-30 15:18 [RFC 00/12] io_uring zerocopy send Pavel Begunkov
2021-11-30 15:18 ` [RFC 01/12] skbuff: add SKBFL_DONT_ORPHAN flag Pavel Begunkov
2021-11-30 15:18 ` [RFC 02/12] skbuff: pass a struct ubuf_info in msghdr Pavel Begunkov
2021-11-30 15:18 ` [RFC 03/12] net/udp: add support msgdr::msg_ubuf Pavel Begunkov
2021-11-30 15:18 ` [RFC 04/12] net: add zerocopy_sg_from_iter for bvec Pavel Begunkov
2021-11-30 15:18 ` [RFC 05/12] net: optimise page get/free for bvec zc Pavel Begunkov
2021-12-01 19:20 ` Jonathan Lemon
2021-12-01 20:17 ` Pavel Begunkov
2021-11-30 15:18 ` [RFC 06/12] io_uring: add send notifiers registration Pavel Begunkov
2021-11-30 15:18 ` [RFC 07/12] io_uring: infrastructure for send zc notifications Pavel Begunkov
2021-11-30 15:18 ` [RFC 08/12] io_uring: wire send zc request type Pavel Begunkov
2021-11-30 15:18 ` [RFC 09/12] io_uring: add an option to flush zc notifications Pavel Begunkov
2021-11-30 15:18 ` [RFC 10/12] io_uring: opcode independent fixed buf import Pavel Begunkov
2021-11-30 15:18 ` [RFC 11/12] io_uring: sendzc with fixed buffers Pavel Begunkov
2021-11-30 15:19 ` [RFC 12/12] io_uring: cache struct ubuf_info Pavel Begunkov
2021-12-01 3:10 ` [RFC 00/12] io_uring zerocopy send David Ahern
2021-12-01 15:32 ` Pavel Begunkov
2021-12-01 17:57 ` David Ahern
2021-12-01 19:11 ` Pavel Begunkov
2021-12-01 19:20 ` David Ahern
2021-12-01 20:15 ` Pavel Begunkov [this message]
2021-12-01 21:51 ` Martin KaFai Lau
2021-12-01 22:35 ` David Ahern
2021-12-01 23:07 ` Martin KaFai Lau
2021-12-01 23:18 ` Pavel Begunkov
2021-12-02 15:48 ` Pavel Begunkov
2021-12-02 17:40 ` Martin KaFai Lau
2021-12-01 20:42 ` Pavel Begunkov
2021-12-01 14:31 ` Pavel Begunkov
2021-12-01 17:49 ` David Ahern
2021-12-01 19:59 ` Pavel Begunkov
2021-12-01 18:10 ` Willem de Bruijn
2021-12-01 19:59 ` Pavel Begunkov
2021-12-01 20:29 ` Pavel Begunkov
2021-12-02 0:36 ` Willem de Bruijn
2021-12-02 16:25 ` Pavel Begunkov
2021-12-02 0:32 ` Willem de Bruijn
2021-12-02 16:45 ` Pavel Begunkov
2021-12-02 21:25 ` Willem de Bruijn
2021-12-03 16:19 ` Pavel Begunkov
2021-12-03 16:30 ` Willem de Bruijn
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=974b266e-d224-97da-708f-c4a7e7050190@gmail.com \
--to=asml.silence@gmail.com \
--cc=axboe@kernel.dk \
--cc=davem@davemloft.net \
--cc=dsahern@gmail.com \
--cc=dsahern@kernel.org \
--cc=edumazet@google.com \
--cc=io-uring@vger.kernel.org \
--cc=jonathan.lemon@gmail.com \
--cc=kuba@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=willemb@google.com \
--cc=yoshfuji@linux-ipv6.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
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;
as well as URLs for NNTP newsgroup(s).