lkml.org 
[lkml]   [2005]   [Nov]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC] [PATCH 00/13] Introduce task_pid api
Quoting Pavel Machek (pavel@ucw.cz):
> Hi!
>
> > > Hmm... it is hard to judge a patch without context. Anyway, can't we
> > > get process snasphot/resume without virtualizing pids? Could we switch
> > > to 128-bits so that pids are never reused or something like that?
> >
> > That might work fine for a managed cluster, but it wouldn't be a good
> > fit if you ever wanted to support something like a laptop in
> > disconnected operation, or if you ever want to restore the same snapshot
> > more than once. There may also be some practical userspace issues
> > making pids that large.
> >
> > I also hate bloating types and making them sparse just for the hell of
> > it. It is seriously demoralizing to do a ps and see
> > 7011827128432950176177290 staring back at you. :)
>
> Well, doing cat /var/something/foo.pid, and seeing pid of unrelated process
> is wrong, too... especially if you try to kill it....

Good point. However the foo.pid scheme is incompatible with
checkpoint/restart and migration regardless.

a. what good is trying to kill something using such a file if
the process is checkpointed+killed, to be restarted later?
b. it is expected that any files used by a checkpointable
processes exist on a network fs, so that the fd can be moved.
What good is foo.pid if it's on a network filesystem?

So if you wanted to checkpoint and restart/migrate a process with a
foo.pid type of file, you might need to start it with a private
tmpfs in a private namespace. That part is trivial to do as part
of the management tools, though checkpointing a whole tmpfs per process
could be unfortunate.

-serge
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-11-20 23:40    [W:0.188 / U:0.448 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site