From 17c5524ada3f2ca9a9c645f540bedc5575302059 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Mon, 3 Apr 2023 19:40:47 -0500 Subject: [PATCH 5/5] nbd/server: Request TCP_NODELAY MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Eric Blake RH-MergeRequest: 274: nbd: improve TLS performance of NBD server RH-Bugzilla: 2035712 RH-Acked-by: Miroslav Rezanina RH-Acked-by: Kevin Wolf RH-Acked-by: Stefano Garzarella RH-Commit: [2/2] 092145077756cda2a4f849c5911031b0fc4a2134 (ebblake/qemu-kvm) 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: <20230404004047.142086-1-eblake@redhat.com> Reviewed-by: Philippe Mathieu-Daudé (cherry picked from commit f1426881a827a6d3f31b65616c4a8db1e9e7c45e) Signed-off-by: Eric Blake --- nbd/server.c | 1 + 1 file changed, 1 insertion(+) diff --git a/nbd/server.c b/nbd/server.c index a5edc7f681..6db124cf53 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -2738,6 +2738,7 @@ 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)); -- 2.39.1