basic power monitoring script

src/quintain-cpu-power-watcher.sh

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+#!/bin/bash
+
+# report power usage in watts over 1 second intervals for each powercap rapl
+# zone
+
+# derived from example at https://www.reddit.com/r/linuxquestions/comments/1dp81bq/hardware_power_consumption/`
+# changes:
+# - some bug fixes in the watts conversion
+# - track each powercap/rapl zone separately, and report its name
+# - use floating point timestamps and calculations
+
+# you can temporarily enable access to the required counters (i.e. on a
+# development laptop) by running the following:
+#
+# sudo chmod -R a+r /sys/class/powercap/intel-rapl
+
+declare -A zones
+declare -A old_zones
+
+old_time=0
+while :; do
+    # figure out how many zones are available; store current microjoules value
+    # for each in an associative array
+    for i in `ls /sys/class/powercap/intel-rapl/ |grep intel-rapl:`; do
+        name=`cat /sys/class/powercap/intel-rapl/$i/name`
+        energy_uj=`cat /sys/class/powercap/intel-rapl/$i/energy_uj`
+        zones[$name]=$energy_uj
+    done
+
+    # current timestamp in seconds and nanoseconds
+    time=$(date +%s.%N)
+
+    if [ ${#old_zones[@]} -ne 0 ]; then
+        # normal case.  calculate power in watts for each zone based on
+        # elapsed time and difference in reported microjoules
+        echo -n "$time"
+        for i in "${!zones[@]}"; do
+            watts=`echo "(${zones[$i]} - ${old_zones[$i]}) / (($time - $old_time) * 10^6)" | bc -l`
+            echo -e -n "\t$watts"
+        done
+        echo -e -n "\n"
+    else
+        # first loop iteration.  we don't have enough data yet to report
+        # watts, but we use this opportunity to print a header row
+        echo -n "# <timestamp>"
+        for i in "${!zones[@]}"; do
+            echo -e -n "\t<$i>"
+        done
+        echo -e -n "\n"
+    fi
+
+    # save old time and microjoules
+    old_time=$time
+    for i in "${!zones[@]}"; do
+        old_zones[$i]=${zones[$i]}
+    done
+
+    # one second interval
+    sleep 1
+done
+