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| author |   Florian Westphal <fw@strlen.de> | 2023-03-24 11:47:20 +0100 |
|---|---|---|
| committer |   Kevin Wolf <kwolf@redhat.com> | 2023-03-27 13:44:29 +0200 |
| commit | bd2cd4a441ded163b62371790876f28a9b834317 (patch) | |
| tree | 0dd59ed051aac73435ed6b2a4a09f23506b83dc7 /scripts/coverage/compare_gcov_json.py | |
| parent | Merge tag 'pull-request-2023-03-24' of https://gitlab.com/thuth/qemu into staging (diff) | |
| download | qemu-bd2cd4a441ded163b62371790876f28a9b834317.tar.xz qemu-bd2cd4a441ded163b62371790876f28a9b834317.zip | |
nbd/server: push pending frames after sending reply
qemu-nbd doesn't set TCP_NODELAY on the tcp socket.
Kernel waits for more data and avoids transmission of small packets.
Without TLS this is barely noticeable, but with TLS this really shows.
Booting a VM via qemu-nbd on localhost (with tls) takes more than
2 minutes on my system. tcpdump shows frequent wait periods, where no
packets get sent for a 40ms period.
Add explicit (un)corking when processing (and responding to) requests.
"TCP_CORK, &zero" after earlier "CORK, &one" will flush pending data.
VM Boot time:
main: no tls: 23s, with tls: 2m45s
patched: no tls: 14s, with tls: 15s
VM Boot time, qemu-nbd via network (same lan):
main: no tls: 18s, with tls: 1m50s
patched: no tls: 17s, with tls: 18s
Future optimization: if we could detect if there is another pending
request we could defer the uncork operation because more data would be
appended.
Signed-off-by: Florian Westphal <fw@strlen.de>
Message-Id: <20230324104720.2498-1-fw@strlen.de>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'scripts/coverage/compare_gcov_json.py')
0 files changed, 0 insertions, 0 deletions