/proc/<PID>/cmdline

Samuli Kaski (samkaski@cs.Helsinki.FI)
Wed, 16 Jul 1997 20:41:10 +0300 (EET DST)


I observed one day how 'w' output brakes if the process (it's PCB?)
got swapped out. Here, look:

samkaski@nat1:~$ ps aux | grep \(
..
samkaski 105 0.0 0.1 1244 60 2 S 13:56 0:00 (startx)
..
samkaski@nat1:~$ cat /proc/105/cmdline ; echo ""

samkaski@nat1:~$
samkaski@nat1:~$ ps aux | grep -- \-bash
..
samkaski 134 0.0 0.8 1548 276 p2 S N 13:56 0:00 -bash
..
samkaski@nat1:~$ cat /proc/134/cmdline ; echo ""
-bash
samkaski@nat1:~$

Now, I understand very well that the processes command line is
swapped out but shouldn't referencing the data cause a page-fault
and make Linux bring the PCB (or the required part of it) to memory?
I mean if /proc is just a mapping of the memory and part of that
memory is on disk shouldn't it be fetched when needed? I'm sorry if
this is a too amateurish question for you kernel hackers out there.

Oops, almost forgot, I'm running 2.0.30

--
Samuli Kaski, samkaski@cs.helsinki.fi
Department of Computer Science, University of Helsinki, Finland.