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    Chris Abbey wrote:
    > Today, Dan Hollis wrote:
    > > but where would the finger start pointing then?
    > hmm... *compiler optimizations* for a specific family cause
    > problems on that family, but *compiler optimizations* for
    > a lesser family don't... I'll admit my kernel h4x0|^ 5k1!!s
    > aren't on par with most on this list, but has anyone thought
    > to take a look at the *compiler optimizations* that are
    > generated?

    It's not the compiler options. (or at least not alone).
    I have proof for this, let me explain:

    For the upcomming Red Hat Linux release an athlon kernel
    will be included, and due to the people who have this
    problem, I added a kernel commandline option to disable
    the optimized page_copy() and clear_page() functions.
    The use of this option makes the machines, of the people
    who had this problem, happy again.

    Now I also wrote the 2 functions in question, and I am
    very convinced that they are correct. They also work on
    the vast majority of motherboards, and most of the failure
    cases are cheaper motherboards (or cheap PSU's).

    The net effect of using the optimized functions is that
    the memory bandwidth the CPU uses effecively doubles during
    COW and page_clear() operations. This puts additional load
    on the motherboard it seems.... I don't know if it's the
    voltage regulators or borderline ram chips that give up,
    but there are people who bought 25 identical machines (for
    a classroom) and only 1 failed, reproducable.

    Oh and btw, having these functions is the main reason for
    enabling the "Athlon" CPU type; that's basically the real
    difference between a PII and Athlon compiled kernel.

    Arjan van de Ven
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