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    SubjectRe: RFC: remove __read_mostly
    On Fri, 14 Dec 2007 01:33:45 +0100 Andi Kleen <andi@firstfloor.org> wrote:

    > Kyle McMartin <kyle@mcmartin.ca> writes:
    >
    > > I'd bet, in the __read_mostly case at least, that there's no
    > > improvement in almost all cases.
    >
    > I bet you're wrong. Cache line behaviour is critical, much more
    > than pipeline behaviour (which unlikely affects). That is because
    > if you eat a cache miss it gets really expensive, which e.g.
    > a mispredicted jump is relatively cheap in comparison. We're talking
    > one or more orders of magnitude.

    So... once we've moved all read-mostly variables into __read_mostly, what
    is left behind in bss?

    All the write-often variables. All optimally packed together to nicely
    maximise cacheline sharing.


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