Re: [RFC v13][PATCH 00/14] Kernel based checkpoint/restart

[Oren Laadan]

Oren Laadan wrote:
> Hi,
> 
> Just got back from 3 weeks with practically no internet, and I see
> that I missed a big party !
> 
> Trying to catch up with what's been said so far --

[...]

>>>>
>>>> - Will any of this involve non-trivial serialisation of kernel
>>>>   objects?  If so, that's getting into the
>>>>   unacceptably-expensive-to-maintain space, I suspect.
>>> We have some structures that are certainly tied to the kernel-internal
>>> ones.  However, we are certainly *not* simply writing kernel structures
>>> to userspace.  We could do that with /dev/mem.  We are carefully pulling
>>> out the minimal bits of information from the kernel structures that we
>>> *need* to recreate the function of the structure at restart.  There is a
>>> maintenance burden here but, so far, that burden is almost entirely in
>>> checkpoint/*.c.  We intend to test this functionality thoroughly to
>>> ensure that we don't regress once we have integrated it.
>> I guess my question can be approximately simplified to: "will it end up
>> looking like openvz"?  (I don't believe that we know of any other way
>> of implementing this?)
>>
>> Because if it does then that's a concern, because my assessment when I
>> looked at that code (a number of years ago) was that having code of
>> that nature in mainline would be pretty costly to us, and rather
>> unwelcome.
> 
> I originally implemented c/r for linux as as kernel module, without
> requiring any changes from the kernel. (Doing the namespaces as a kernel
> module was much harder). For more details, see:
> 	https://www.ncl.cs.columbia.edu/research/migrate

oops... I meant the following link:
	http://www.ncl.cs.columbia.edu/research/migration/

see, for example, the papers from DejaView (SOSP 07) and Zap (USENIX 07).

Oren.


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