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([2001:b07:6468:f312:9af8:e5f5:7516:fa89]) by smtp.googlemail.com with ESMTPSA id v7-20020a170906564700b009447277c26fsm5999210ejr.72.2023.04.04.06.49.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 Apr 2023 06:49:06 -0700 (PDT) Message-ID: <2d2d0705-b5eb-b3b6-f558-3d460db58729@redhat.com> Date: Tue, 4 Apr 2023 15:49:05 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH v2 for 8.0?] nbd/server: Request TCP_NODELAY Content-Language: en-US To: Eric Blake , qemu-devel@nongnu.org Cc: Florian Westphal , Vladimir Sementsov-Ogievskiy , "open list:Network Block Dev..." References: <20230404004047.142086-1-eblake@redhat.com> From: Paolo Bonzini In-Reply-To: <20230404004047.142086-1-eblake@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -39 X-Spam_score: -4.0 X-Spam_bar: ---- X-Spam_report: (-4.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-1.925, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org 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 > Signed-off-by: Eric Blake > 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? > > 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)); > > base-commit: efcd0ec14b0fe9ee0ee70277763b2d538d19238d Acked-by: Paolo Bonzini