I’m talking about these things here:

Proper time on wikipedia:

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Linux process user time:

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this is because this is the passing of time as seen by the process itself, not by an external observer. i.e. an external observer might measure absolute time (from their point of view) but time passes at a different speed (slower, in most cases) as experienced by the process itself. this is because it continues to sleep repeatedly, and so it doesn’t wake up and do things, so it occupies fewer CPU cycles and it experiences less time itself.