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

Message ID 20230404144244.185609-2-eblake@redhat.com
State New
Headers show
Series [PULL,1/1] nbd/server: Request TCP_NODELAY | expand

Commit Message

Eric Blake April 4, 2023, 2:42 p.m. UTC 
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(+)
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Patch

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));