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73 lines
2.4 KiB
73 lines
2.4 KiB
From 170872370c6f3c916e741eb32d80431995d7a870 Mon Sep 17 00:00:00 2001
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From: Florian Westphal <fw@strlen.de>
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Date: Fri, 24 Mar 2023 11:47:20 +0100
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Subject: [PATCH 4/5] nbd/server: push pending frames after sending reply
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RH-Author: Eric Blake <eblake@redhat.com>
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RH-MergeRequest: 274: nbd: improve TLS performance of NBD server
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RH-Bugzilla: 2035712
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>
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RH-Commit: [1/2] ab92c06c48810aa40380de0433dcac4c6e4be9a5 (ebblake/qemu-kvm)
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qemu-nbd doesn't set TCP_NODELAY on the tcp socket.
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Kernel waits for more data and avoids transmission of small packets.
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Without TLS this is barely noticeable, but with TLS this really shows.
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Booting a VM via qemu-nbd on localhost (with tls) takes more than
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2 minutes on my system. tcpdump shows frequent wait periods, where no
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packets get sent for a 40ms period.
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Add explicit (un)corking when processing (and responding to) requests.
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"TCP_CORK, &zero" after earlier "CORK, &one" will flush pending data.
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VM Boot time:
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main: no tls: 23s, with tls: 2m45s
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patched: no tls: 14s, with tls: 15s
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VM Boot time, qemu-nbd via network (same lan):
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main: no tls: 18s, with tls: 1m50s
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patched: no tls: 17s, with tls: 18s
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Future optimization: if we could detect if there is another pending
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request we could defer the uncork operation because more data would be
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appended.
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Signed-off-by: Florian Westphal <fw@strlen.de>
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Message-Id: <20230324104720.2498-1-fw@strlen.de>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Reviewed-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit bd2cd4a441ded163b62371790876f28a9b834317)
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Signed-off-by: Eric Blake <eblake@redhat.com>
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---
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nbd/server.c | 3 +++
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1 file changed, 3 insertions(+)
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diff --git a/nbd/server.c b/nbd/server.c
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index 4630dd7322..a5edc7f681 100644
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--- a/nbd/server.c
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+++ b/nbd/server.c
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@@ -2647,6 +2647,8 @@ static coroutine_fn void nbd_trip(void *opaque)
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goto disconnect;
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}
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+ qio_channel_set_cork(client->ioc, true);
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+
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if (ret < 0) {
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/* It wans't -EIO, so, according to nbd_co_receive_request()
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* semantics, we should return the error to the client. */
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@@ -2672,6 +2674,7 @@ static coroutine_fn void nbd_trip(void *opaque)
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goto disconnect;
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}
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+ qio_channel_set_cork(client->ioc, false);
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done:
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nbd_request_put(req);
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nbd_client_put(client);
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--
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2.39.1
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