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    SubjectRe: x86 ptep_get_and_clear question


    On Fri, 16 Feb 2001, Manfred Spraul wrote:
    >
    > That leaves msync() - it currently does a flush_tlb_page() for every
    > single dirty page.
    > Is it possible to integrate that into the mmu gather code?

    Not even necessary.

    The D bit does not have to be coherent. We need to make sure that we flush
    the TLB before we start the IO on the pages which clears the per-physical
    D bit (so that no CPU will have done any modifications that didn't show up
    in one of the D bits - whther virtual in the page tables or physical in
    the memory map), but there are no other real requirements.

    So you don't strictly need to gather them at all, although right now with
    the type of setup we have I suspect it's hard to actually implement any
    other way (because msync doesn't necessarily know when the IO has been
    physically started and has no good way of hooking into it..).

    Linus

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