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    SubjectRe: [LKML] Re: [PATCH v3] ad7877: keep dma rx buffers in seperate cache lines
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    On Wed, 12 May 2010 00:35:45 -0400
    Mike Frysinger <vapier.adi@gmail.com> wrote:

    > On Tue, May 11, 2010 at 23:23, FUJITA Tomonori wrote:
    > > Seems that kmalloc is not cacheline aligned on some architectures but
    > > they works. Probably, we might be just lucky because in general they
    > > allocate larger buffers than 64 for DMA via kmalloc and the buffers
    > > are aligned on the size?
    >
    > i think the magic combo is:
    > - DMA buffer is written to (receive)
    > - some driver state is in the same cacheline as the DMA buffer
    > - that driver state is used after the flush but before the DMA finishes
    > - only on arches that need software cache coherency
    >
    > so i could see this not being an obvious issue for many people

    Yeah, we don't hit such condition everyday. And as I said, SCSI
    usually uses kmalloc'ed buffers rather than the cache size (buffers
    are aligned on roundup_pow_of_two(the allocated size)). But I think
    that we want to fix this issue explicitly. I guess that it would be
    better to start a new thread about this issue.


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