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    SubjectDo we need to call calibrate_delay() for all cores/hyperthreads on a socket?

    I do not know all the different combinations of sockets, cores, and
    hyperthreads out there, but it seems like all cores and their hyperthreads
    on a socket should compute the same value for their calculate_delay()

    When booting a 4096 cpu system without specifying lpj on the command line,
    we spend approximately 0.1 seconds per core/hyperthread calculating the
    lpj value for that cpu.

    If we were to, on the other hand, only calculate the delay value for the
    first core on a socket, we would reduce the time spent booting a 4096 cpu
    (256 sockets, 8 cores per socket hyperthreaded) down from nearly seven
    minutes to approx 25 seconds. This seems like a very safe optimization,
    but I repeat that I do not know all the different potential combinations
    of socket, core, hyperthread out that. Please note these are just rough
    approximations taken from memory. I am doing a couple of test boots
    now without and with lpj= specified on the command line to get a more
    accurate approximation.

    Robin Holt

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      Last update: 2010-12-03 07:55    [W:0.056 / U:41.168 seconds]
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