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    SubjectRe: [PATCH] 2.6 workaround for Athlon/Opteron prefetch errata
    Date
    In article <3F6087FC.7090508@pobox.com>,
    Jeff Garzik <jgarzik@pobox.com> wrote:
    | Andi Kleen wrote:
    | > It was not created for that (I know that because I created it ;-)
    |
    | hehe
    |
    |
    | > X86_GENERIC is merely an optimization hint (currently it only changes the cache
    | > line size hint) It does not change anything related to correctness. Everything
    | > that handles correctness is checked unconditionally.
    |
    | When, building non-Pentium4-related code when CONFIG_MPENTIUM4 &&
    | !CONFIG_X86_GENERIC, it's OK that the code is incorrect for (picking
    | example) AMD processors.
    |
    | It would be a user bug to boot that on an AMD box, just like it would be
    | user bug to boot a CONFIG_M586 kernel on an ancient 386.
    |
    |
    | > is_prefetch is a correctness thing.
    |
    | When we know at compile time it's not needed, it should not be enabled.

    Clearly that's right. This buys nothing on CPUs which don't have the
    problem, why have *any* overhead in size and speed? It's too bad that
    people have to read around all that code, they don't need to give it a
    home in their RAM and execute it as well.
    --
    bill davidsen <davidsen@tmr.com>
    CTO, TMR Associates, Inc
    Doing interesting things with little computers since 1979.
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