Incoming: UDP parallel input

UDP input is about to become faster and parallel on OpenBSD. In a message to tech@ titled UDP parallel input, Alexander Bluhm (bluhm@) offers a diff that enables parallel UDP input for -current.

The message reads,

List:       openbsd-tech
Subject:    UDP parallel input
From:       Alexander Bluhm <bluhm () openbsd ! org>
Date:       2024-07-23 13:40:21

Hi,

mvs@ has completed the final bits to make socket buffer MP safe for
UDP packets.  This means that we can run UDP input on multiple
threads.  Diff below activates this.

Usually IP processing runs on multiple softnet threads with shared
net lock.  From there local packets are queued and processed by one
thread with exclusive net lock.  If the PR_MPINPUT flag is set,
protocol input is called directly from IP input on multiple threads,
shared net lock and no additional queueing.

Note that you need kernel sources from at least Sun Jul 21.  Then
apply this diff and test UDP local delivery to sockets.  To see an
performance effect, you need multiple CPUs and network interfaces
that support multiqueue.  These are bnxt, igc, ix, ixl, ngbe, vmx.

Please test!

bluhm

followed by the rather short diff that enables the code.

This is (yet another) opportunity to test and help improve the upcoming release if you feel up to it.

Update 2024-07-26: The code has now been committed.