/proc/<pid>/stat children CPU time

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http://serverfault.com – I've been running the following command on my linux box: watch -d -n 1 "cat /proc/19866/stat" The pid above is a pid of Nginx's master process - I would expect the following fields to be changing: 14, 15, 16 and 17 as according to kernel docs those should contain amount of time the process has been scheduled in user/kernel mode (14,15) and its children too (16,17), however running this command in watch I noticed that none of those numbers ever change. Can someone shed a bit more light on this ? I'd like to count some CPU usage stats per process and I thought /proc.. was the place to look. T (HowTos)