Messages in this thread | | | Subject | Re: [RFC][PATCH 1/2] Track in-kernel when we expect checkpoint/restart to work | From | Greg Kurz <> | Date | Fri, 10 Oct 2008 18:34:49 +0200 |
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On Fri, 2008-10-10 at 11:17 -0400, Oren Laadan wrote: > > Ingo Molnar wrote: > > * Daniel Lezcano <dlezcano@fr.ibm.com> wrote: > > > >>> By the way, why don't you introduce the reverse operation ? > >> I think implementing the reverse operation will be a nightmare, IMHO > >> it is safe to say we deny checkpointing for the process life-cycle > >> either if the created resource was destroyed before we initiate the > >> checkpoint. > > > > it's also a not too interesting case. The end goal is to just be able to > > checkpoint everything that matters - in the long run there simply wont > > be many places that are marked 'cannot checkpoint'. > > > > So the ability to deny a checkpoint is a transitional feature - a > > flexible CR todo list in essence - but also needed for > > applications/users that want to rely on CR being a dependable facility. > > > > It would be bad for most of the practical usecases of checkpointing to > > allow the checkpointing of an app, just to see it break on restore due > > to lost context. > > Actually it need not wait for restore to fail - it can fail during the > checkpoint, as soon as the unsupported feature is encountered. >
Of course, bad things must be spotted at checkpoint time ! :)
> Adding that flag of what you suggest will help make it more vocal and > obvious that a feature isn't supported, even without the user actually > trying to take a checkpoint. I like that I idea. >
This flag is weak... testing it gives absolutly no hint whether the checkpoint may succeed or not. As it is designed now, a user can only be aware that checkpoint is *forever* denied. I agree that it's only useful as a "flexible CR todo list".
In the long run, if there are still things that can prevent checkpoint from being consistent, they will have to be checked at checkpoint time.
Greg.
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