Re: [PATCH v2 for 8.0?] nbd/server: Request TCP_NODELAY

[Philippe Mathieu-Daudé]

On 4/4/23 02:40, Eric Blake wrote:
> 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: <20230327192947.1324372-1-eblake@redhat.com>
> ---
>
> v2 fix typo, enhance commit message
>
> Given that corking made it in through Kevin's tree for 8.0-rc2 but
> this one did not, but I didn't get any R-b, is there any objection to
> me doing a pull request to get this into 8.0-rc3?

FWIW, no objection.

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

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>