Am 24.03.2023 um 11:47 hat Florian Westphal geschrieben: > 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 <f...@strlen.de>
Thanks, applied to the block branch. Kevin
