Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Tue, 28 Dec 2021 18:40:18 +0100 | Subject | Re: cpufreq: intel_pstate: map utilization into the pstate range |
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On Tue, Dec 28, 2021 at 5:58 PM Julia Lawall <julia.lawall@inria.fr> wrote: > > I looked a bit more into why pstate 20 is always using the least energy. I > have just one thread spinning for 10 seconds, I use a fixed value for the > pstate, and I measure the energy usage with turbostat.
How exactly do you fix the pstate?
> I tried this on a > 2-socket Intel 6130 and a 4-socket Intel 6130. The experiment runs 40 > times. > > There seem to be only two levels of CPU energy usage. On the 2-socket > machine the energy usage is around 600J up to pstate 20 and around 1000J > after that. On the 4-socket machine it is twice that.
These are the package power numbers from turbostat, aren't they?
> The change in RAM energy usage is similar, eg around 320J for the 2-socket > machine up to pstate 20, and around 460J for higher pstates. > > On the 6130, pstate 21 is 2.1GHz, which is the nominal frequency of the > machine. So it seems that the most efficient thing is to be just below > that. The reduced execution time with pstate 20 as compared to pstate 10 > greatly outweighs any small increase in the energy usage due to changing > the frequency. > > Perhaps there is something abnormal in how the machines are configured?
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