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    SubjectRe: sched_domains and Stream benchmark
    On Tue, Apr 27, 2004 at 09:47:19AM -0700, Darren Hart wrote:
    > On Mon, 2004-04-26 at 19:33, Andi Kleen wrote:
    > > > I noticed your binary ran with N=2000000 which is only sufficient for a
    > > > 2 proc 1 MB cache opteron box according to the documentation on the
    > >
    > > It does not seem to make any difference.
    >
    > I was under the impression you didn't change the N value (array size)
    > and ran the benchmark with someone else's precompiled binaries (the ones
    > you sent me). Did you have two binaries with different array sizes

    Correct. I always used 2000000. But it did not seem to make
    any difference in showing the scheduler issues even when going
    to 4 CPUs.

    (there were some fluctuations, but much less than the 25% you reported)

    > > > stream faq. I also noticed wide variation in results (25% or so) when
    > > > running with 4 threads on a 4 proc opteron on linux-2.6.5-mm5. Can you
    > > > provide me with the specs of the system you ran your tests on?
    > >
    > > Yes, mm5 is still broken because it has the "tuned to numasaurus" numa
    > > scheduler. Run it on a standard (non mm*) kernel or with Ingo's early
    > > load balance patch.
    >
    > I ran it on 2.6.5, 2.6.5-mm5, and 2.6.5-mm5-flat-domains trying to
    > reproduce the results you found (including the poor performance of
    > virgin and mm) so that I can have some context while analyzing the
    > sched_domains topology on x86_64 and its effects on performance. So
    > that I can see where the differences lie in our tests, could you please
    > provide some of the specs of the system you ran on, such as number of
    > procs, cache size, and amount of RAM.

    I saw the issue on a wide range of systems, ranging from 2 CPUs to 4 CPUs.
    All hard enough per CPU memory to fit the benchmark.

    -Andi
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