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    SubjectRe: [RFC PATCH 27/28] sunrpc: Use sendmsg(MSG_SPLICE_PAGES) rather then sendpage
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    Chuck Lever III <chuck.lever@oracle.com> 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/

    > 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

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