Subject: Re: [RFC v7][PATCH 2/9] General infrastructure for checkpoint
	restart
From: Dave Hansen <dave@linux.vnet.ibm.com>
To: Daniel Jacobowitz <dan@debian.org>
Cc: Oren Laadan <orenl@cs.columbia.edu>, linux-api@vger.kernel.org,
       containers@lists.linux-foundation.org, mingo@elte.hu,
       linux-kernel@vger.kernel.org, linux-mm@kvack.org,
       viro@zeniv.linux.org.uk, hpa@zytor.com,
       Andrew Morton <akpm@linux-foundation.org>,
       torvalds@linux-foundation.org, tglx@linutronix.de
In-Reply-To: <20081022025513.GA7504@caradoc.them.org>
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Date: Tue, 21 Oct 2008 20:02:43 -0700
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On Tue, 2008-10-21 at 22:55 -0400, Daniel Jacobowitz wrote:
> I haven't been following - but why this whole container restriction?
> Checkpoint/restart of individual processes is very useful too.
> There are issues with e.g. IPC, but I'm not convinced they're
> substantially different than the issues already present for a
> container.

Containers provide isolation.  Once you have isolation, you have a
discrete set of resources which you can checkpoint/restart.

Let's say you have a process you want to checkpoint.  If it uses a
completely discrete IPC namespace, you *know* that nothing else depends
on those IPC ids.  We don't even have to worry about who might have been
using them and when.

Also think about pids.  Without containers, how can you guarantee a
restarted process that it can regain the same pid?

-- Dave

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