Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH RFC 0/3] Per-process power consumption measurement facility | Date | Tue, 30 Jul 2013 15:31:50 +0200 |
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On Tuesday, July 30, 2013 10:52:56 AM Peter Zijlstra wrote: > On Tue, Jul 30, 2013 at 12:17:36PM +0400, Konstantin Krivyakin wrote: > > This patchset adds per-process power consumption measurement facility. > > Power consumption is very important on mobile platforms. This code > > allows to measure consumed power in Watts*Hours. The consumed power > > for process is updated on scheduler switch and depends on current > > CPU voltage and frequency. > > > > The formula for computation is: P = C * V^2 * f, where C is a constant > > that reflects capacity of the system, V is the current voltage and > > f is the current frequency. > > (Taken from: http://en.wikipedia.org/wiki/CPU_power_dissipation). > > > > In this patchset was added implementation for Exynos platform > > to demonstrate how it works. > > > > To minimize scheduler impact for each CPU P-state the value of (V^2 *f) > > was precomputed at the time of platform initialization. > > It seems to me the 3 multiplies that takes could be done when cpufreq > actually changes the P-state. > > > And to reduce performance impact furthermore, the C constant is multiplied > > in userspace. > > That seems particularly silly; how is userspace to know C and why > isn't it a much better idea to do this in the code generating the number > for userspace to consume. > > Also, I intensely dislike this thing because: > > - it adds more user interface > - it adds more accounting muck > - it completely lacks any useful changelogs > - it completely fails to even begin addressing the issues we already > have with cpufreq > > There's been a lot of talk about power aware scheduling in the recent > past, there's also been a lot of problems listed we must overcome/solve. > This patch set completely fails to tie into any of that. > > You also completely fail to explain the user case and thus related why > you can't use any of the other facilities like perf or ftrace to measure > this.
Agreed, thanks Peter!
-- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.
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