IORING_OP_SENDMSG_FIXED + IORING_OP_RECVMSG_FIXED

[Victor Stewart <v@nametag.social>]

Hello all my name is Victor Stewart.

I just mentioned to Jens on Twitter how fixed sendmsg and recvmsg
would be fantastic additions for burgeoning QUIC traffic.

We have MSG_ZEROCOPY, but it's fairly dead on arrival. For one, it's
only on the send side. It also involves locking pages into memory for
each send. Testing has shown it's only worth using for >10KB sends,
and even still only improves production traffic by single digit %s
(cite LWN).

so Jens suggested I post here to see if anyone is already working on
this. And if not, if someone would like to collaborate?

I've never contributed to the kernel before so I wouldn't know where
to begin with tooling, testing and guidelines, but I would enjoy
learning by doing.

Probably a weekend's work. Seems trivial enough to flag msg_iov as
within a registered buffer, on the back of fixed reads and writes. The
rest of msghdr is doubtfully worth the aggravation.

V