Threads and processes

David Smith DavidSmith at byu.net
Tue Mar 1 15:02:08 MST 2005


Here are two process questions for the kernel heads:

1. I am developing a multi-threaded app in C++ for Linux. Under RHEL 3.0,
when I do 'ps -A', my app shows up just once, but under Debian Unstable,
'ps -A' shows 10 (the number of threads I have). Can someone explain why
this is? I remember studying kernel-level threads and user-level threads
in my OS class, but why would two Linux kernels behave differently? Is it
just a matter of differing ps options perhaps?

2. The one process on RHEL has a VSZ that is about double the Debian VSZ
(as shown by 'ps -eo vsz'). I would have expected it to be 10 times as
large, since it is "hiding" 10 processes in 1.

Here is some more info that may help:

Debian Unstable:

  $ uname -a
  Linux localhost 2.4.27-1-686 #1 Wed Dec 1 19:57:47 JST 2004 i686 GNU/Linux
  $ ps -eo comm,vsz | grep myprog
  myprog 90608

RHEL 3.0:

  $ uname -a
  Linux localhost 2.4.21-4.EL #1 Fri Oct 3 18:13:58 EDT 2003 i686 i686 i386
  GNU/Linux
  $ ps -eo vsz | grep myprog
  myprog 43748
  myprog 43748
  myprog 43748
  myprog 43748
  <snip/>

Thanks!

--Dave



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