Re: C/R without "leaks"

Nathan Lynch
2009-04-22T00:16:29Z

Oren Laadan <orenl@cs.columbia.edu> writes:
> Alexey Dobriyan wrote:
>>> Again, so to checkpoint one task in the topmost pid-ns you need to
>>> checkpoint (if at all possible) the entire system ?!
>>
>> One more argument to not allow "leaks" and checkpoint whole container,
>> no ifs, buts and woulditbenices.
>>
>> Just to clarify, C/R with "leak" is for example when process has separate
>> pidns, but shares, for example, netns with other process not involved in
>> checkpoint.
>>
>> If you allow this, you lose one important property of checkpoint part,
>> namely, almost everything is frozen. Losing this property means suddenly
>> much more stuff is alive during dump and you has to account to more stuff
>> when checkpointing. You effectively checkpointing on live data structures
>> and there is no guarantee you'll get it right.
>
> Alexey, we're entirely on par about this: everyone agrees that if you
> want the maximal guarantee (if one exists) you must checkpoint entire
> container and have no leaks.
>
> The point I'm stressing is that there are other use cases, and other
> users, that can do great things even without full container. And my
> goal is to provide them this capability.

As it seems that Alexey's goal is more or less a subset of yours, would
it make sense in the near term to concentrate on getting an
implementation upstream that satisfies that subset (i.e. checkpoint on a
container basis only)? And then support for checkpointing arbitrary
processes could be added later, if it proves feasible?