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    SubjectRe: [PATCH] 2.6 workaround for Athlon/Opteron prefetch errata
    On Sun, 14 Sep 2003, Zwane Mwaikambo wrote:

    > On Sun, 14 Sep 2003, bill davidsen wrote:
    >
    > > We just got a start on making Linux smaller to encourage embedded use, I
    > > don't see adding 300+ bytes of wasted code so people can run
    > > misconfigured kernels.
    > >
    > > I rather have to patch this in for my Athlon kernels than have people
    > > who aren't cutting corners trying to avoid building matching kernels
    > > have to live with the overhead.
    >
    > Overhead? Really you could save more memory by cleaning up a lot of
    > drivers. Andi already said it before, there are better places to be
    > looking at.

    The best way to remove overhead is not to add it. Putting in 300+ bytes of
    code which is pure overhead on anything but an Athlon is silly. And to
    justify it because it save effort for people who don't want to bother
    building the correct distribution is pure hubris. The Athlon is not so
    important that making it run a tiny bit faster justifies taking extra
    space on every machine which doesn't benefit.
    >
    > Also 'patching' for Athlon kernels doesn't cut it for people who need to
    > distribute kernels which run on various hardware (such as distros). This
    > alone is benefit enough to justify this supposed 'bloat'.

    You clearly think that a kernel will not run on Athlon without this
    patch. In real life kernel built for 386, 486, Ppro, etc will run
    nicely on every CPU except those less featureful, including the
    precious Athlon.

    That being the case, there is no justification for forcing the code on
    every build rather than putting ifdefs around it. Any vendor who wants
    to make Athlon a tiny bit faster at the expense of making every other
    system use more memory for code which is never executed can just use the
    config option to include the support.

    Let's try the facts agin:
    1 - the code is not needed for Athlon, prefetch is turned off on broken
    CPUs now. A generic kernel runs fine on Athlon.
    2 - the discussion is not on having the code or not, but on putting
    ifdefs around this code so it is only generated if wanted.

    Let's not continue to pollute the kernel with architecture dependent
    code, we have subtrees for that.

    --
    bill davidsen <davidsen@tmr.com>
    CTO, TMR Associates, Inc
    Doing interesting things with little computers since 1979.

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