That's one of the specific exceptions he mentions. Behavioral changes happen, and maybe we don't even support some feature any more. There's a number

That's one of the specific exceptions he mentions. Behavioral changes happen, and maybe we don't even support some feature any more. There's a number of fields in /proc/<pid>/stat that are printed out as zeroes, simply because they don't even *exist* in the kernel any more, or because showing them was a mistake (typically an information leak). But the numbers got replaced by zeroes, so that the code that used to parse the fields still works. i.e. the kernel may not do what it did before but your tool shouldn't crash. It may not have all the info you used to see though ... Edit: fix styling