Messages in this thread | | | Date | Thu, 31 Mar 2011 08:50:36 +0200 | From | Ingo Molnar <> | Subject | Re: [RFC 2/2] Make x86 calibrate_delay run in parallel. |
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* 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.
Thanks,
Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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