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    SubjectRe: [PATCH 0/5][RFC] Fallocate Volatile Ranges v6
    Hi John,

    On Fri, Jul 27, 2012 at 8:57 PM, John Stultz <> wrote:
    > So after not getting too much positive feedback on my last
    > attempt at trying to use a non-shrinker method for managing
    > & purging volatile ranges, I decided I'd go ahead and try
    > to implement something along Minchan's ERECLAIM LRU list
    > idea.

    Agree that there hasn't been much feedback from MM folks yet - sorry
    about that :/

    I think one issue might be that most people don't have a good
    background on how the feature is intended to be used, and it is very
    difficult to comment meaningfully without that.

    As for myself, I have been wondering:

    - Why the feature needs to be on a per-range basis, rather than
    per-file. Is this simply to make it easier to transition the android
    use case from whatever they are doing right now, or is it that the
    object boundaries within a file can't be known in advance, and thus
    one wouldn't know how to split objects accross different files ? Or
    could it be that some of the objects would be small (less than a page)
    so space use would be inefficient if they were placed in different
    files ? Or just that there would be too many files for efficient
    management ?

    - What are the desired semantics for the volatile objects. Can the
    objects be accessed while they are marked as volatile, or do they have
    to get unmarked first ? Is it really the case that we always want to
    reclaim from volatile objects first, before any other kind of caches
    we might have ? This sounds like a very strong hint, and I think I
    would be more comfortable with something more subtle if that's
    possible. Also, if we have several volatile objects to reclaim from,
    is it desirable to reclaim from the one that's been marked volatile
    the longest or does it make no difference ? When an object is marked
    volatile, would it be sufficient to ensure it gets placed on the
    inactive list (maybe with the referenced bit cleared) and let the
    normal reclaim algorithm get to it, or is that an insufficiently
    strong hint somehow ?

    Basically, having some background information of how android would be
    using the feature would help us better understand the design decision
    here, I think.

    Michel "Walken" Lespinasse
    A program is never fully debugged until the last user dies.

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