Hi Rafael, On 2020.11.30 10:37 Rafael J. Wysocki wrote:
> First off, some cpufreq drivers (eg. intel_pstate) can pass hints > beyond the current target frequency to the hardware and there are no > provisions for doing that in the cpufreq framework. In particular, > today the driver has to assume that it should allow the frequency to Forgot the important "not": today the driver has to assume that it should allow not the frequency to > fall below the one requested by the governor (or the required capacity > may not be provided) which may not be the case and which may lead to > excessive energy usage in some scenarios. > > Second, the hints passed by these drivers to the hardware neeed not s/neeed/need ... O.K. this is good. The problem with my basic CPU frequency verses load test with the schedutil governor is that it is always so oscillatory it is pretty much not possible to conclude anything. So I re-worked the test to look at Processor Package Power load instead. In a previous e-mail [1] I had reported the power differences for one periodic load at one frequency, as a (apparently cherry picked) example. Quoted: > schedutil governor: > acpi-cpufreq: good > intel_cpufreq hwp: bad <<<<< Now good, with this patch set. > intel_cpufreq no hwp: good > ... > periodic workflow at 347 hertz. > ~36% load at 4.60 GHz (where hwp operates) > ~55% load at 3.2 GHz (where no hwp operates) > > intel_cpufreq hwp: 9.6 processor package watts. 45.8 watts on the mains to > the computer. > intel_cpufreq no hwp: ~6 processor package watts. ~41 watts on the mains to > the computer. (noisy) So this time, I only have power/energy data, and a relatively easy way to compress all 12,000 samples into some concise summary is to simply find the average power for the entire experiment: Legend: hwp: Kernel 5.10-rc6, HWP enabled; intel_cpufreq; schedutil (always) rjw: Kernel 5.10-rc6 + this patch set, HWP enabled; intel_cpu-freq; schedutil no-hwp: Kernel 5.10-rc6, HWP disabled; intel_cpu-freq; schedutil acpi-cpufreq: Kernel 5.10-rc6, HWP disabled; acpi-cpufreq; schedutil load work/sleep frequency: 73 Hertz: hwp: Average: 12.00822 watts rjw: Average: 10.18089 watts no-hwp: Average: 10.21947 watts acpi-cpufreq: Average: 9.06585 watts load work/sleep frequency: 113 Hertz: hwp: Average: 12.01056 rjw: Average: 10.12303 no-hwp: Average: 10.08228 acpi-cpufreq: Average: 9.02215 load work/sleep frequency: 211 Hertz: hwp: Average: 12.16067 rjw: Average: 10.24413 no-hwp: Average: 10.12463 acpi-cpufreq: Average: 9.19175 load work/sleep frequency: 347 Hertz: hwp: Average: 12.34169 rjw: Average: 10.79980 no-hwp: Average: 10.57296 acpi-cpufreq: Average: 9.84709 load work/sleep frequency: 401 Hertz: hwp: Average: 12.42562 rjw: Average: 11.12465 no-hwp: Average: 11.24203 acpi-cpufreq: Average: 10.78670 [1] https://marc.info/?l=linux-pm&m=159769839401767&w=2 My tests results graphs: Note: I have to code the web site, or I get hammered by bots. Note: it is .com only because it was less expensive than .org 73 Hertz: Double u double u double u dot smythies dot .com/~doug/linux/s18/hwp/k510-rc6/su73/ 113 Hertz: Double u double u double u dot smythies dot .com/~doug/linux/s18/hwp/k510-rc6/su113/ 211 Hertz: Double u double u double u dot smythies dot .com/~doug/linux/s18/hwp/k510-rc6/su211/ 347 Hertz: Double u double u double u dot smythies dot .com/~doug/linux/s18/hwp/k510-rc6/su347/ 401 Hertz: Double u double u double u dot smythies dot .com/~doug/linux/s18/hwp/k510-rc6/su401/ ... Doug
