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    SubjectRe: [PATCH 00 of 12] mmu notifier #v13

    I believe the differences between your patch set and Christoph's need
    to be understood and a compromise approach agreed upon.

    Those differences, as I understand them, are:

    1) invalidate_page: You retain an invalidate_page() callout. I believe
    we have progressed that discussion to the point that it requires some
    direction for Andrew, Linus, or somebody in authority. The basics
    of the difference distill down to no expected significant performance
    difference between the two. The invalidate_page() callout potentially
    can simplify GRU code. It does provide a more complex api for the
    users of mmu_notifier which, IIRC, Christoph had interpretted from one
    of Andrew's earlier comments as being undesirable. I vaguely recall
    that sentiment as having been expressed.

    2) Range callout names: Your range callouts are invalidate_range_start
    and invalidate_range_end whereas Christoph's are start and end. I do not
    believe this has been discussed in great detail. I know I have expressed
    a preference for your names. I admit to having failed to follow up on
    this issue. I certainly believe we could come to an agreement quickly
    if pressed.

    3) The structure of the patch set: Christoph's upcoming release orders
    the patches so the prerequisite patches are seperately reviewable
    and each file is only touched by a single patch. Additionally, that
    allows mmu_notifiers to be introduced as a single patch with sleeping
    functionality from its inception and an API which remains unchanged.
    Your patch set, however, introduces one API, then turns around and
    changes that API. Again, the desire to make it an unchanging API was
    expressed by, IIRC, Andrew. This does represent a risk to XPMEM as
    the non-sleeping API may become entrenched and make acceptance of the
    sleeping version less acceptable.

    Can we agree upon this list of issues?

    Thank you,
    Robin Holt


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