[LBo] About /proc/uptime [was: Chap 3 - Exercises]

[Stefan Waidele]

Anita Lewis schrieb:
> [...]
> 'man proc' lists all those cute little files and somewhere in there is
> the part for uptime:
> 
>      /proc/uptime
>               This file contains two numbers: the uptime of the  system
> (sec‐
>               onds), and the amount of time spent in idle process (seconds).
> 
> And I don't know what idle process is, but I could see that it was not
> changing as I looked at the file off and on over time, while the first
> number did change as the seconds rolled by.

The "idle-process" is the process that runs when there is nothing to be 
done. A CPU cannot do "nothing". Well, probably, it can (modern 
power-management), but usually it needs to do stuff, and if it is only 
to "go to the next command".

If there is no process requesting the CPU, then the idle-process is 
being run.

So if the two numbers displayed by "cat /proc/uptime" are almost equal, 
then your system is idle most of the time.

Anita's "idle-count" does not increase because she is running folding at 
home at a very low priority. FaH _always_ has something to do, so on her 
system, the idle-process is not being executed much. It is only run 
when/if there is absolutely nothing to do and FaH needs to wait for some 
I/O call to return...


Making sense?

Stefan