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Subject: Re: [Ksummit-2010-discuss] checkpoint-restart: naked patch
From: Nathan Lynch <ntl@pobox.com>
To: Tejun Heo <tj@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Oren Laadan <orenl@cs.columbia.edu>,
        ksummit-2010-discuss@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, kapil@ccs.neu.edu, gene@ccs.neu.edu
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 <1288835258.6132.56.camel@tp-t61>  <4CD26270.5050906@kernel.org>
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Date: Thu, 04 Nov 2010 15:45:37 -0500
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On Thu, 2010-11-04 at 08:36 +0100, Tejun Heo wrote:
> Hello,
> 
> On 11/04/2010 02:47 AM, Nathan Lynch wrote:
> >>   In this case whitelisting the allowed
> >> state by requiring special APIs for all I/O (or even just standard
> >> APIs as long as they are supposed by the C/R lib you're linked against)
> >> is the more pragmatic, and I think faithful aproach.
> > 
> > I don't think users will go for it.  They'll continue to use dodgy
> > out-of-tree kernel modules and/or LD_PRELOAD hacks instead of porting
> > their applications to a new library.  I think a C/R library is an
> > "ideal" solution, but it's one that nobody would use - especially in
> > HPC, unless the library somehow provides better performance.
> 
> I hear that there are plans to integrate one of the userland
> snapshotting implementations with HPC workload manager.  ISTR the
> combination to be condor + dmtcp but not sure.  I think things like
> that make a lot of sense.

If you look at the C/R implementations of those two projects you'll see
that they don't implement what I take to be hch's suggestion - a library
or platform with special-purpose APIs to which applications are ported
in order to gain C/R ability.  For all their good points, the projects
you mention do interposition for glibc's syscall wrappers and provide a
few optional hooks so apps can control certain aspects of C/R.


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