Introduction
------------

The purpose of idlestat is to measure how long we have been in the different
idle and operating states.

Idlestat uses kernel's FTRACE function to monitor and capture C-state and
P-state transitions of CPUs over a time interval. It extracts the following
information from trace file:
	- Times when CPUs entered and exited a certain C-state
	- Times when CPUs entered and exited a certain P-state
	- Raised IRQs

Following a successful run, idlestat calculates and reports the following
information:
	- Total, average, minimum and maximum time spent in each C-state,
	per-CPU.
	- Total, average, minimum and maximum time spent in each P-state,
	per-CPU.
	- Total, average, minimum and maximum time during which all CPUs in
	a cluster were in the same C-state, per-cluster.
	- Number of times a certain IRQ caused a CPU to exit idle state,
	per-CPU and per-IRQ

Requirements
------------

1. It must be run as root in order to access /sys/kernel/debug.
2. It requires tracing to be enabled in the kernel.

Also, IPI reporting requires appropriate tracepoints in the kernel.
This is available for ARM and ARM64 since v3.17-rc1.  A patch for X86
was submitted but still not merged upstream.  It can be retrieved here:
https://lkml.org/lkml/2014/9/17/745

Help
----
./idlestat -h will show all the options

Example Usage
-------------

Trace mode:
sudo ./idlestat --trace -f /tmp/mytrace -t 10

Reporting mode (/tmp/mytrace already contains traces):
sudo ./idlestat --import -f /tmp/mytrace

Trace mode with workload (e.g. sleep, cyclictest):
sudo ./idlestat --trace -f /tmp/mytrace -t 10 -- /bin/sleep 10
sudo ./idlestat --trace -f /tmp/myoutput -t 10 -- cyclictest -t 4 -i 2000 -q -D 5

Selective trace output
sudo ./idlestate --import -f /tmp/mytrace -w
sudo ./idlestate --import -f /tmp/mytrace -c -p
sudo ./idlestate --import -f /tmp/mytrace -p -w