Re: [Containers] [PATCH 6/7] vt: Update spawnpid to be a struct pid_t

From: Kirill Korotaev
Date: Wed Aug 16 2006 - 03:59:55 EST

Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> writes:

Ar Maw, 2006-08-15 am 12:23 -0600, ysgrifennodd Eric W. Biederman:

This keeps the wrong process from being notified if the
daemon to spawn a new console dies.

Not sure why we count pids not task structs but within the proposed
implementation this appears correct so

Basically struct pid is relatively cheap, 64bytes or so.
struct task is expensive 10K or so, when all of the stacks
and everything are included.

Counting pids allows the task to exit in user space and free up
all of it's memory.

When /proc used to count the task struct it was fairly easy to
deliberately oom a 32bit machine just by open up directories in
/proc and then having the process exit. rlimits didn't help because
we don't count processes that have exited.
hey, hey. your patch doesn't help in this situation (much)!
inodes and dentries can still consume much memory.
it just makes the situation a bit better.

I wonder whether it is easy to have the following done with your implementation:
container tasks visible from host. theoretically having 2 pids (vpid, pid)
it should be implementable. Do you see any obstacles?

in other regards patches look pretty good. Good job!


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