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    SubjectRe: [rfc][patch] mm: madvise(WILLNEED) for anonymous memory
    On Thu, Dec 20, 2007 at 05:53:41PM +0100, Peter Zijlstra wrote:
    >
    > On Thu, 2007-12-20 at 15:26 +0000, Hugh Dickins wrote:
    >
    > > The asynch code: perhaps not worth doing for MADV_WILLNEED alone,
    > > but might prove useful for more general use when swapping in.
    > > Not really the same as Con's swap prefetch, but worth looking
    > > at that for reference. But I guess this becomes a much bigger
    > > issue than you were intending to get into here.
    >
    > heh, yeah, got somewhat more complex that I'd hoped for.
    >
    > last patch for today (not even compile tested), will do a proper patch
    > and test it tomorrow.
    >
    > ---
    > A best effort MADV_WILLNEED implementation for anonymous memory.
    >
    > It adds a batch method to the page table walk routines so we can
    > copy a few ptes while holding the kmap, which makes it possible to
    > allocate the backing pages using GFP_KERNEL.

    Yuck. We actually need to just fix the atomic kmap issue in the
    existing pagemap code rather than add a new method, I think.

    If performance of map/unmap is too slow at a granularity of 1, we can
    add some internal batching in the CONFIG_HIGHPTE case.

    --
    Mathematics is the supreme nostalgia of our time.


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