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    SubjectRe: RFC: CONFIG_PAGE_SHIFT (aka software PAGE_SIZE)
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    On Sat, 2007-07-07 at 00:26 +0200, Andrea Arcangeli wrote:
    > for the hack week at opensuse (see http://idea.opensuse.org/) I've
    > been working on a new feature called CONFIG_PAGE_SHIFT.
    ...
    > If you want to help/look here the patch:
    >
    > http://www.kernel.org/pub/linux/kernel/people/andrea/patches/v2.6/2.6.22-rc7/hard-page-size
    >
    > I'm tracking it with hg mq extension so far, but I can change if it
    > helps.

    The patch looks really interesting, it's just a little hard to parse
    with all of the s/4096/PAGE_SIZE/ bits around. Those cleanups, along
    with the s/PAGE_SIZE/HARD_PAGE_SIZE/ parts would be great in a
    separated-out patch so that the really juicy bits (like the pte
    handling) where the new logic is stand out better.

    I think it would help readability to have something like:

    #define PAGES_PER_HARD_PAGE (1<<(PAGE_SHIFT-HARD_PAGE_SHIFT))

    which would look like this:

    - if (unlikely(!pfn_valid(pfn))) {
    + if (unlikely(!pfn_valid(pfn * PAGES_PER_HARD_PAGE))) {

    Instead of having hardpfn_t, would it be more useful to tag the types
    with sparse? That's probably something that other interested parties
    could work on.

    -- Dave

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