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[176.184.5.132]) by smtp.gmail.com with ESMTPSA id m2-20020a5d4a02000000b002d75ef32032sm11645924wrq.68.2023.04.04.01.11.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 Apr 2023 01:11:42 -0700 (PDT) Message-ID: <7e5598a3-cc72-a375-105a-93bf4976206e@linaro.org> Date: Tue, 4 Apr 2023 10:11:40 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.9.1 Subject: Re: [PATCH v2 for 8.0?] nbd/server: Request TCP_NODELAY 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> Content-Language: en-US From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= In-Reply-To: <20230404004047.142086-1-eblake@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::42a; envelope-from=philmd@linaro.org; helo=mail-wr1-x42a.google.com X-Spam_score_int: -33 X-Spam_score: -3.4 X-Spam_bar: --- X-Spam_report: (-3.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-1.349, RCVD_IN_DNSWL_NONE=-0.0001, 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? FWIW, no objection. > nbd/server.c | 1 + > 1 file changed, 1 insertion(+) Reviewed-by: Philippe Mathieu-Daudé