[RFC 0/6] implement io_uring notification (ubuf_info) stacking

Pavel Begunkov
2024-04-12T12:55:34Z

io_uring allocates a ubuf_info per zerocopy send request, it's convenient
for the userspace but with how things are it means that every time the
TCP stack has to allocate a new skb instead of amending into a previous
one. Unless sends are big enough, there will be lots of small skbs
straining the stack and dipping performance.

The patchset implements notification, i.e. an io_uring's ubuf_info
extension, stacking. It tries to link ubuf_info's into a list, and
the entire link will be put down together once all references are
gone.

Testing with liburing/examples/send-zerocopy and another custom made
tool, with 4K bytes per send it improves performance ~6 times and
levels it with MSG_ZEROCOPY. Without the patchset it requires much
larger sends to utilise all potential.

bytes | before | after (Kqps)
100 | 283 | 936
1200 | 195 | 1023
4000 | 193 | 1386
8000 | 154 | 1058

Pavel Begunkov (6):
net: extend ubuf_info callback to ops structure
net: add callback for setting a ubuf_info to skb
io_uring/notif: refactor io_tx_ubuf_complete()
io_uring/notif: remove ctx var from io_notif_tw_complete
io_uring/notif: simplify io_notif_flush()
io_uring/notif: implement notification stacking

drivers/net/tap.c | 2 +-
drivers/net/tun.c | 2 +-
drivers/vhost/net.c | 8 +++-
include/linux/skbuff.h | 21 ++++++----
io_uring/notif.c | 91 +++++++++++++++++++++++++++++++++++-------
io_uring/notif.h | 13 +++---
net/core/skbuff.c | 37 +++++++++++------
7 files changed, 129 insertions(+), 45 deletions(-)

--
2.44.0