Add platform-independent per-process power policy

[wentasah]

This is just a simple modification of imx8-per-process. If it works well, we'll replace imx8-per-process with this platform independent policy.

[wentasah]

@benedond Can you test this on both TX2 and i.MX8? If it works well, we remove the imx8-specific policy and replace it with this.

[benedond]

I am just trying to run some configuration at TX2. I am getting:

root@tegra-ubuntu:~/experiments/20_test_demos# ./run_tx2.sh 
Cooling down to 60°C, current Cortex_A57_temp temperature: 35.5°C, time: 0s...
Done
Opening ./test_tx2.csv
Running: demos-sched -p imx8_per_process -c config_tx2.yaml
0.0s  35.5°C   >>> 09:56:13.895 [info] Activating power management (power policy: 'imx8_per_process', args: '')
>>> 09:56:13.917 [error] Exception: Failed to initialize power policy imx8_per_process: map::at

It should be the current demos compiled from per-process branch.

[wentasah]

Don't use -p imx8_per_process, but -p per_process.

[benedond]

How are the frequencies currently handled? It seems that there might be some problem with conversion/rounding.

Listing the frequencies out on tx2 gives:

345600 499200 652800 806400 960000 1113600 1267200 1420800 1574400 1728000 1881600 2035200

I suppose that DEmOS handles them in MHz, so I set, e.g., 345 as the lowest one. This gives the following exception:

>>> 10:24:03.749 [error] Exception: Attempted to set CPU frequency for `policy0` to `345000000` Hz, which is less than the supported minimum of `345600000` Hz

Ok, I set it to 345.6, which in turn gives:

>>> 10:27:16.212 [error] Exception: yaml-cpp: error at line 5, column 38: bad conversion

It seems that floats are not supported, so I change the config to 346, in that case, the program complains again:

>>> 10:29:12.792 [error] Exception: Attempted to set CPU frequency for `policy0` to `346000000` Hz, but this CPU supports only the following frequencies: ~345 MHz, ~499 MHz, ~652 MHz, ~806 MHz, 960 MHz, ~1113 MHz, ~1267 MHz, ~1420 MHz, ~1574 MHz, 1728 MHz, ~1881 MHz, ~2035 MHz

[MatejKafka]

DEmOS internally uses frequencies in Hz, but the config format accepts uints interpreted as MHz.

https://github.com/CTU-IIG/demos-sched/blob/master/src/config.cpp#L441 https://github.com/CTU-IIG/demos-sched/blob/master/src/config.cpp#L507 https://github.com/CTU-IIG/demos-sched/blob/master/src/cpufreq_policy.hpp#L40

I think it should be enough to adjust these 3 lines to switch to kHz/Hz or accept float values. Also, some test configs in test_config may need adjustment if the units are changed.

EDIT: also these two: https://github.com/CTU-IIG/demos-sched/blob/master/src/config.cpp#L73 https://github.com/CTU-IIG/demos-sched/blob/master/src/config.cpp#L214

[wentasah]

@benedond I've added the required changes to this PR (mainly commit df48116), but there seems to be another problem: #67.

[benedond]

I am still testing the freq. setting under DEmOS on TX2. Currently, I am unable to run the test script due to some discrepancy between the available frequencies and maximal allowed frequency.

Available frequencies according to /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies are

345600 499200 652800 806400 960000 1113600 1267200 1420800 1574400 1728000 1881600 2035200 

Current settings before the experiment show:

>>> root@tegra-ubuntu:~/experiments/20_test_demos# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
2035200
>>> root@tegra-ubuntu:~/experiments/20_test_demos# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq 
345600
>>> root@tegra-ubuntu:~/experiments/20_test_demos# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
ondemand

But then I run demos-sched and get the following error complaining about supported maximum being 1420800:

root@tegra-ubuntu:~/experiments/20_test_demos# ./run_tx2.sh 
Cooling down to 60°C, current Cortex_A57_temp temperature: 37.5°C, time: 0s...
Done
Opening ./test_tx2.csv
Running: demos-sched -p per_process -c config_tx2.yaml
0.0s  37.5°C   >>> 07:33:38.600 [info] Activating power management (power policy: 'per_process', args: '')
>>> 07:33:38.648 [error] Exception: Attempted to set CPU frequency for `policy1` to `1574400000` Hz, which is more than the supported maximum of `1420800000` Hz

Frequencies 1574400 1728000 1881600 2035200 are not allowed by demos-sched for some reason even though the demos-sched itself hints them whenever some frequency is set in a wrong way:

>>> 07:17:11.578 [error] Exception: Attempted to set CPU frequency for `policy0` to `346000000` Hz, but this CPU supports only the following frequencies: 345.6 MHz, 499.2 MHz, 652.8 MHz, 806.4 MHz, 960 MHz, 1113.6 MHz, 1267.2 MHz, 1420.8 MHz, 1574.4 MHz, 1728 MHz, 1881.6 MHz, 2035.2 MHz

[wentasah]

Probably some stupidity in NVIDIA's cpufreq driver. Does it work if you comment out the following code? https://github.com/CTU-IIG/demos-sched/blob/df48116528bf13dfdd2472764e2906ba4b98562b/src/cpufreq_policy.hpp#L184-L189

[MatejKafka]

Probably some stupidity in NVIDIA's cpufreq driver. Does it work if you comment out the following code?

https://github.com/CTU-IIG/demos-sched/blob/df48116528bf13dfdd2472764e2906ba4b98562b/src/cpufreq_policy.hpp#L184-L189

The bounds are also enforced by the cpufreq interface, as you probably already found out, so this will just error out with some IO error. :)

[wentasah]

The bounds are also enforced by the cpufreq interface, as you probably already found out, so this will just error out with some IO error. :)

No. At least on TX2, we verified that you are allowed to write a higher frequency manually without any error, but the actual frequency stays at what is set in scaling_max_freq.

[MatejKafka]

Oh, right, not enforced, but clamped.