/proc/stat/ includes the following fields:


Which subset of those fields + idle accounts for 100% CPU? Is there some overlap, or should the total of all fields always be 100% of CPU time?


It should be that system + user + idle = 100% (those are about CPU time). As long as you have got 1 CPU only (lately unlikely, even my cellphone has two cores ;-). The sar(1) command (on Fedora part of the sysstat package) summarizes this kind of data, it's manpage might be of further help.


I always use user + system + nice + idle + iowait == 100%.

On some systems, there's also "steal" which is typically if the OS is running in a VM.

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