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    SubjectRe: [PATCH v3] ad7877: keep dma rx buffers in seperate cache lines
    On Tue, May 11, 2010 at 09:42:03AM +0300, Pekka Enberg wrote:
    > Hi Dmitry,
    >
    > On Tue, May 11, 2010 at 9:33 AM, Dmitry Torokhov
    > <dmitry.torokhov@gmail.com> wrote:
    > >> what guarantee exactly do you have for that statement ?
    > >
    > > The data is kmalloced, kmalloc aligns on cacheline boundary AFAIK which
    > > means that next kmalloc data chunk will not share "our" cacheline.
    >
    > No, there are no such guarantees. kmalloc() aligns on
    > ARCH_KMALLOC_MINALIGN or ARCH_SLAB_MINALIGN depending on which is
    > bigger but beyond that, there are no guarantees. You can, of course,
    > use kmem_cache_create() with SLAB_HWCACHE_ALIGN to align on cacheline
    > boundary.
    >

    The architectures that we are trying to deal with here should be forcing
    kmalloc to the cache boundary already though - otherwise they would not
    be able to used kmalloced memory for DMA buffers at all. Or am I utterly
    lost here?

    --
    Dmitry


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