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    SubjectRe: [PATCH 2/2] x86: replace BIO_VMERGE_BOUNDARY with BIOVEC_PHYS_MERGEABLE
    Ingo Molnar wrote:
    > * FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:
    >
    >
    >> On Mon, 27 Oct 2008 12:57:00 +0100
    >> Jens Axboe <jens.axboe@oracle.com> wrote:
    >>
    >>
    >>> On Mon, Oct 27 2008, Jeremy Fitzhardinge wrote:
    >>>
    >>>> Jens Axboe wrote:
    >>>>
    >>>>> Pretty much baffles me as well, xen should just need to do
    >>>>>
    >>>>> #define BIOVEC_PHYS_MERGEABLE(vec1, vec2) 0
    >>>>>
    >>>>>
    >>>> It needs to be a runtime switch, since we only want to do this when
    >>>> actually running under Xen. Also, its possible that the two pages might
    >>>> actually be physically contiguous, so they could be merged anyway.
    >>>>
    >>> Alright, then add a xen_biovec_phys_mergeable(vec1, vec2) in the xen
    >>> code that actually checks this for real. You can add your switch there
    >>> as well. Then put the BIOVEC_PHYS_MERGEABLE() in the xen arch includes,
    >>> done.
    >>>
    >>> What Tomo is saying is that this has nothing to do with virtual merging,
    >>> and he's right.
    >>>
    >> Yeah, overriding BIOVEC_PHYS_MERGEABLE perfectly works for Xen. And it
    >> is not related with BIO_VMERGE_BOUNDARY at all.
    >>
    >> Ingo, please put this patch into your tree:
    >>
    >> http://marc.info/?l=linux-kernel&m=122482703716620&w=2
    >>
    >
    > does it have any dependency on:
    >
    > Subject: [PATCH 1/2] bio: define __BIOVEC_PHYS_MERGEABLE
    >

    No, they're independent. Defining __BIOVEC_PHYS_MERGEABLE will be
    useful for the Xen changes I need to make in the wake of Tomo's patch.

    J


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