Chuck Lever III [off-list ref] wrote:

That means I haven't seen the cover letter and do not have any
context for this proposed change.

https://lore.kernel.org/linux-fsdevel/20230316152618.711970-1-dhowells@redhat.com/ (local)

We've tried combining the sendpages calls in here before. It
results in a significant and measurable performance regression.
See:

da1661b93bf4 ("SUNRPC: Teach server to use xprt_sock_sendmsg for socket sends")

The commit replaced the use of sendpage with sendmsg, but that took away the
zerocopy aspect of sendpage.  The idea behind MSG_SPLICE_PAGES is that it
allows you to do keep that.  I'll have to try reapplying this commit and
adding the MSG_SPLICE_PAGES flag.

Therefore, this kind of change needs to be accompanied by both
benchmark results and some field testing to convince me it won't
cause harm.

Yep.

And, we have to make certain that this doesn't break operation
with kTLS sockets... do they support MSG_SPLICE_PAGES ?

I haven't yet tackled AF_TLS, AF_KCM or AF_SMC as they seem significantly more
complex than TCP and UDP.  I thought I'd get some feedback on what I have
before I tried my hand at those.

David