Experiment to measure video playback power efficiency vs CPU frequency, with performance and schedutil governors

sample_results.dat

# freq performance_watt schedutil_watt
2000 19.31 18.38
2100 17.49 19.23
2200 18.47 18.70
2300 19.69 18.27
2400 19.89 18.53
2500 20.56 19.00
2600 19.01 18.35
2700 20.87 19.11
2800 21.05 18.85
2900 19.50 18.36
3000 20.85 19.74
3100 21.28 19.57
3200 19.69 19.16
3300 21.79 18.57
3400 22.29 19.16
3500 22.90 19.20
3600 23.53 19.24
3700 24.13 19.42
3800 23.11 18.77
3900 23.81 18.19
4000 25.27 18.52
4100 27.28 19.78
4200 28.17 19.32

video_playback_efficiency.bash

#!/bin/bash

testvid="/tmp/vid/testvid.webm"
mhz_lo=2000
mhz_hi=4200

ncpu=$(grep -c processor /proc/cpuinfo)

measure_power () {
        stress -q -c $ncpu -t 10 # preheat the die/IHS for 10 seconds
        sudo turbostat \
            --quiet --Summary --show PkgWatt --out "/tmp/turbostat.out" \
            -- \
            mpv \
                --no-terminal --ao=null --fs \
                --start=00:00:10 --length=60 "$testvid"
        tail -n1 "/tmp/turbostat.out"
        sudo rm "/tmp/turbostat.out"
}

collect () {
    echo "please make sure screensaver is suspended"
    sudo -v
    # preheat the CPU heatsink for 2 minutes
    sudo cpupower frequency-set -g performance -u 2000MHz
    stress -c $ncpu -t 120
    # clear old results
    truncate --size 0 results.dat
    # Test frequencies in random order
    for mhz in $(seq "$mhz_lo" 100 "$mhz_hi" | shuf); do
        sudo cpupower frequency-set -g schedutil -u "${mhz}MHz"
        pow_schedutil="$(measure_power)"
        sudo cpupower frequency-set -g performance -u "${mhz}MHz"
        pow_performance="$(measure_power)"
        printf "%s %s %s\n" "$mhz" "$pow_performance" "$pow_schedutil" \
            >>"results.dat"
    done
    # put results in frequency order
    sort -o "results.dat" "results.dat"
}

plot () {
    gnuplot <<EOF
        set terminal pngcairo size 800,600
        set output "plot.png"
        set xlabel "MHz"
        set ylabel "Watts"
        set autoscale x noextend 
        set xtics 200 rotate by -45 offset -1
        plot "results.dat" using 1:2 with linespoints title "performance", \
            "" using 1:3 with linespoints title "schedutil"
EOF
}

collect
plot