This means we have to read the values from /proc/stat on a fixed interval and calculate the delta from these readings. The CPU usage can be measured over an interval of time only. If you are interested in these values, take a look on /proc/interrupts which does not only show the counters but also the CPU mapping too. The following counters are the count for each possible system interrupt.

The first column of the 'intr' line is the total of all interrupts served on the system since boot time. USER_HZ is a compile time constant which can be queried using: ShellĬonst double ticks = (double)sysconf( _SC_CLK_TCK ) The time is measured in USER_HZ (also called Jiffies) which are typically 1/100ths of a second. Time spent for running a virtual CPU or guest OS under the control of the kernel. Time stolen by other operating systems running in a virtual environment. See the description of the intr line for more details.

Time spent in vacations twiddling thumbs. Time spent with niced processes in user mode.

Time spent with normal processing in user mode. The numbers behind the 'cpu' lines identify the amount of time the CPU has spent performing different kind of work: Column The number of 'cpuN' lines is equal to the number of CPUs reported on /proc/cpuinfo. The first 'cpu' line is an aggregate of all following 'cpuN' lines. Depending on the kernel version and the available CPUs on your system, the information shown on /proc/stat may differ slightly. This brings us directly to the first interesting value 'btime' which gives the UNIX epoch time the system was booted.

The /proc/stat file holds various pieces of information about the kernel activity and is available on every Linux system.

Linux cpu utilization