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    SubjectRe: Minutes from Feb 21 LSE Call
    >> OK, so now you've slid from talking about PCs to 2-way to 4-way ...
    >> perhaps because your original arguement was fatally flawed.
    > oh, come on. the issue is whether memory is fast and flat.
    > most "scalability" efforts are mainly trying to code around the fact
    > that any ccNUMA (and most 4-ways) is going to be slow/bumpy.

    Scalability is not just NUMA machines by any stretch of the imagination.
    It's 2x, 4x, 8x SMP as well.

    > it is reasonable to worry that optimizations for imbalanced machines
    > will hurt "normal" ones. is it worth hurting uni by 5% to give
    > a 50% speedup to IBM's 32-way? I think not, simply because
    > low-end machines are more important to Linux.

    We would never try to propose such a change, and never have.
    Name a scalability change that's hurt the performance of UP by 5%.
    There isn't one.

    > ccNUMA worst-case latencies are not much different from decent
    > cluster (message-passing) latencies. getting an app to work on a cluster
    > is a matter of programming will.

    It's a matter of repeatedly reimplementing a bunch of stuff in userspace,
    instead of doing things in kernel space once, properly, with all the
    machine specific knowledge that's needed. It's *so* much easier to
    program over a single OS image.


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