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    SubjectRe: [RFC 2/2] Make x86 calibrate_delay run in parallel.

    * Ingo Molnar <mingo@elte.hu> wrote:

    >
    > * Yinghai Lu <yinghai@kernel.org> wrote:
    >
    > > On Tue, Dec 14, 2010 at 5:58 PM, <Robin@sgi.com> wrote:
    > > >
    > > > On a 4096 cpu machine, we noticed that 318 seconds were taken for bringing
    > > > up the cpus.  By specifying lpj=<value>, we reduced that to 75 seconds.
    > > > Andi Kleen suggested we rework the calibrate_delay calls to run in
    > > > parallel.  With that code in place, a test boot of the same machine took
    > > > 61 seconds to bring the cups up.  I am not sure how we beat the lpj=
    > > > case, but it did outperform.
    > > >
    > > > One thing to note is the total BogoMIPS value is also consistently higher.
    > > > I am wondering if this is an effect with the cores being in performance
    > > > mode.  I did notice that the parallel calibrate_delay calls did cause the
    > > > fans on the machine to ramp up to full speed where the normal sequential
    > > > calls did not cause them to budge at all.
    > >
    > > please check attached patch, that could calibrate correctly.
    > >
    > > Thanks
    > >
    > > Yinghai
    >
    > > [PATCH -v2] x86: Make calibrate_delay run in parallel.
    > >
    > > On a 4096 cpu machine, we noticed that 318 seconds were taken for bringing
    > > up the cpus. By specifying lpj=<value>, we reduced that to 75 seconds.
    > > Andi Kleen suggested we rework the calibrate_delay calls to run in
    > > parallel.
    >
    > The risk wit tat suggestion is that it will spectacularly miscalibrate on
    > hyperthreading systems.

    s/wit tat/with that

    Thanks,

    Ingo
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