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    SubjectRe: [PATCH 1/1] x86: fix text_poke


    On Fri, 25 Apr 2008, Andi Kleen wrote:
    >
    > Not sure how the fixmap is better. It's pretty much equivalent, isn't it?
    > Perhaps a little cheaper, but the code shouldn't be performance critical.

    I have no really strong opinions. However, we do have a *lot* of lock
    prefixes in the kernel, and fixmaps are a lot cheaper than vmap(). It may
    not be performance-critical, but for me the "locks" section for the kernel
    is 0x8060 bytes long, which would seem to say that this is called four
    thousand times for each suspend and resume.

    With each invocation being thousands of instructions and a cross-CPU IPI
    for the tlb flush, that kind of stuff adds up. We're likely talking real
    fractions of a second, rather than milliseconds.

    But no, I didn't time it or really think very deeply about it.

    Linus


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