On 4/13/24 18:17, David Ahern wrote:
On 4/12/24 6:55 AM, Pavel Begunkov wrote:
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 ubuf_info forces TCP segmentation at less than MTU boundaries which
kills performance with small message sizes as TCP is forced to send
small packets. This is an interesting solution to allow the byte stream
to flow yet maintain the segmentation boundaries for callbacks.
Thanks, I'll add your reviews if the patches survive in the
current form!
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(-)
--
Pavel Begunkov
