cpufreq-aperf: add page (#1865)

pages/linux/cpufreq-aperf.md

@@ -0,0 +1,20 @@
+# cpufreq-aperf
+
+> Calculate the average CPU frequency over a time period.
+> Requires root privileges.
+
+- Start calculating, defaulting to all CPU cores and 1 second refresh interval:
+
+`sudo cpufreq-aperf`
+
+- Start calculating for CPU 1 only:
+
+`sudo cpufreq-aperf -c {{1}}`
+
+- Start calculating with a 3 seconds refresh interval for all CPU cores:
+
+`sudo cpufreq-aperf -i {{3}}`
+
+- Calculate only once:
+
+`sudo cpufreq-aperf -o`