[torquedev] job vs. session

Garrick Staples garrick at clusterresources.com
Tue Aug 1 15:02:41 MDT 2006


On Tue, Aug 01, 2006 at 02:49:09PM -0700, Diwaker Gupta alleged:
> Hi all,
> 
> Exactly what is the difference between a job and a session? I couldn't
> find any concrete documentation on them. I'm more interested in an
> implementation oriented definition -- for Linux, it seems like jobs
> are executed within processes, and sessions are denoted by PIDs. So
> are sessions simply the execution containers of jobs? Can there be
> multiple jobs per session or vice-versa?
> 
> My apologies if this is common knowledge.

"session" is a Unix term that binds processes together for the purposes
of signal propogation.  It is similar to, but different from, process
"groups".

See the setsid(2) and setpgid(2) manpages for details.

In pbs_server, only jobs are tracked.

Since pbs_mom has to actually keep track of, and control, individual
processes, a finer-grain control is necessary.  The job has top-level
process (the user's shell) that belongs to seperate session.  The
resources used by the entire session (the user's shell and all child
processes) are counted.



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