Messages in this thread | | | Date | Sun, 20 Nov 2005 16:38:29 -0600 | From | "Serge E. Hallyn" <> | Subject | Re: [RFC] [PATCH 00/13] Introduce task_pid api |
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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.
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