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    SubjectRe: Does pci_alloc_consisent really need to zero memory?
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       From: "Adam J. Richter" <adam@yggdrasil.com>
    Date: Thu, 30 May 2002 02:11:12 -0700

    Is it really necessary for pci_alloc_consistent() to
    fill the memory that it returns with all zeroes? I don't
    see anything in Documentation/DMA-mapping.txt that specifies
    it. I have been on the lookout for drivers that rely on it
    for the past couple of months, and I haven't seen any. It's
    only one line of code in arch/i386/kernel/pci-dma.c, but it
    is potentially a lot of cycles, even if only zeroes the
    space you requested (rather than the full pages that it
    actually allocates).

    pci_alloc_consistent is so rare, I doubt it matters performance
    wise.

    I'd rather see a patch to DMA-mapping.txt that specifies the memory
    returned is zeroed out, as this is what every implementation appears
    to do.
    -
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