[PULL 0/1] NBD patches for 8.0-tc3

[PULL 0/1] NBD patches for 8.0-tc3

[Eric Blake]

The following changes since commit 51a6dc9d394098e8f4141fad869a1ee9585f54f8:

  Merge tag 'pull-target-arm-20230403' of https://git.linaro.org/people/pmaydell/qemu-arm into staging (2023-04-03 17:01:47 +0100)

are available in the Git repository at:

  https://repo.or.cz/qemu/ericb.git tags/pull-nbd-2023-04-04

for you to fetch changes up to f1426881a827a6d3f31b65616c4a8db1e9e7c45e:

  nbd/server: Request TCP_NODELAY (2023-04-04 08:13:15 -0500)

----------------------------------------------------------------
nbd patches for 2023-04-04

- Eric Blake: use TCP_NODELAY in nbd server, as followup to corking

----------------------------------------------------------------
Eric Blake (1):
      nbd/server: Request TCP_NODELAY

 nbd/server.c | 1 +
 1 file changed, 1 insertion(+)

base-commit: 51a6dc9d394098e8f4141fad869a1ee9585f54f8
-- 
2.39.2

[PULL 1/1] nbd/server: Request TCP_NODELAY

[Eric Blake]

Nagle's algorithm adds latency in order to reduce network packet
overhead on small packets.  But when we are already using corking to
merge smaller packets into transactional requests, the extra delay
from TCP defaults just gets in the way (see recent commit bd2cd4a4).

For reference, qemu as an NBD client already requests TCP_NODELAY (see
nbd_connect() in nbd/client-connection.c); as does libnbd as a client
[1], and nbdkit as a server [2].  Furthermore, the NBD spec recommends
the use of TCP_NODELAY [3].

[1] https://gitlab.com/nbdkit/libnbd/-/blob/a48a1142/generator/states-connect.c#L39
[2] https://gitlab.com/nbdkit/nbdkit/-/blob/45b72f5b/server/sockets.c#L430
[3] https://github.com/NetworkBlockDevice/nbd/blob/master/doc/proto.md#protocol-phases

CC: Florian Westphal <fw@strlen.de>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20230404004047.142086-1-eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 nbd/server.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/nbd/server.c b/nbd/server.c
index 848836d4140..3d8d0d81df2 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -2758,6 +2758,7 @@ void nbd_client_new(QIOChannelSocket *sioc,
     }
     client->tlsauthz = g_strdup(tlsauthz);
     client->sioc = sioc;
+    qio_channel_set_delay(QIO_CHANNEL(sioc), false);
     object_ref(OBJECT(client->sioc));
     client->ioc = QIO_CHANNEL(sioc);
     object_ref(OBJECT(client->ioc));
-- 
2.39.2

Re: [PULL 0/1] NBD patches for 8.0-tc3

[Peter Maydell]

On Tue, 4 Apr 2023 at 15:43, Eric Blake <eblake@redhat.com> wrote:
>
> The following changes since commit 51a6dc9d394098e8f4141fad869a1ee9585f54f8:
>
>   Merge tag 'pull-target-arm-20230403' of https://git.linaro.org/people/pmaydell/qemu-arm into staging (2023-04-03 17:01:47 +0100)
>
> are available in the Git repository at:
>
>   https://repo.or.cz/qemu/ericb.git tags/pull-nbd-2023-04-04
>
> for you to fetch changes up to f1426881a827a6d3f31b65616c4a8db1e9e7c45e:
>
>   nbd/server: Request TCP_NODELAY (2023-04-04 08:13:15 -0500)
>
> ----------------------------------------------------------------
> nbd patches for 2023-04-04
>
> - Eric Blake: use TCP_NODELAY in nbd server, as followup to corking
>
> ----------------------------------------------------------------


Applied, thanks.

Please update the changelog at https://wiki.qemu.org/ChangeLog/8.0
for any user-visible changes.

-- PMM