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@@ -0,0 +1,41 @@ +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 + +Example Usage +------------- + +./idlestat -d -o myoutput -t 10 + +where, + +-d : dump the states at the end +-o : output file to store the traces +-t : the duration in seconds + |