Paul Lutus wrote:
> Rick DeNatale wrote:
> 
> / ...
> 
>> By the way, is the actual meaning of user, system, total, and real
>> documented anywhere.  I've looked around a few times, and haven't
>> uncovered it.  I guess I could try to devine it by reading the code
>> for benchmark, but...
> 
> System time is time spent outside userspace, e.g. direct kernel calls.
> User time is time spent directly executing user code in userspace.
> 
> I think total time and real time are self-explanatory, but just in case ...
> total time is system + user + kernel overhead not properly accounted for,
> and real time is simply an RTC measurement at the end of the process life
> subtracted from the same at the beginning. It is expected (in a manner of
> speaking) that none of these quantities will add as one would expect.
> 

I actually dug into this a few weeks ago for the RHEL 3 version of the
2.4.21 Linux kernel. It's mildly complicated and changes from version to
version of the Linux kernel, especially the scheduler. And the external
tools don't always "do the right thing" either. And I *only* looked at
Linux; I'm not in possession of the same information for BSD or MacOS. I
can probably track it down for Windows, however -- it's documented in
Mark Friedman's book in the Windows 2003 Server Resource Kit.

M. Edward "That Guy" Borasky

P.S.: Paul's response is essentially correct and "close enough for all
practical purposes". I get paid to care about the cases when it isn't. :)