Messages in this thread | | | Date | Tue, 14 Apr 2009 10:29:51 -0500 | From | "Serge E. Hallyn" <> | Subject | Re: [PATCH 10/30] cr: core stuff |
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Quoting Oren Laadan (orenl@cs.columbia.edu): > > Hi, > > Serge E. Hallyn wrote: > > Quoting Alexey Dobriyan (adobriyan@gmail.com): > > > > Hi Alexey, > > > > as far as I can see, the main differences between this patch and the > > equivalent in Oren's tree are: > > > > 1. kernel auto-selects container init to freeze > > Actually, this eliminates the possibility to checkpoint a subtree of > tasks, which (under some obvious constraints) can be a handy feature.
Yes, I agree. As Dave pointed out on irc yesterday, this patch shows a very definate whole-container-only point of view which is worth discussing.
> > 2. kernel freezes tasks > > IMHO better to do it in userspace - that way userspace can accomplish > other tasks while tasks are frozen, such as snapshot the filesystem, > or block/unblock the network.
That's a good point.
> Is there a good argument to do it kernel ?
Convenience? I guess you don't have to worry about getting your checkpoint job into a cgroup by itself ahead of time.
> > 3. no objhash taking references > > 4. no hbuf > > 5. always require CAP_SYS_ADMIN > > I'm now convinced (thanks, Serge!) that it's better not to require > this unless we strictly have to.
:) Cool.
I think the perceived need for it comes, as above, from the pure checkpoint-a-whole-container-only view. So long as you will checkpoint/restore a whole container, then you'll end up doing something requiring privilege anyway. But that is not all of the use cases.
-serge
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