Messages in this thread | | | From | Andrey Mirkin <> | Subject | Re: [Devel] Re: [PATCH 0/9] OpenVZ kernel based checkpointing/restart | Date | Mon, 27 Oct 2008 18:07:12 +0400 |
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On Monday 20 October 2008 19:55 Dave Hansen wrote: > On Mon, 2008-10-20 at 16:14 +0400, Andrey Mirkin wrote: > > Right now my patchset (v2) provides an ability to checkpoint and restart > > a group of processes. The process of checkpointing and restart can be > > initiated from external process (not from the process which should be > > checkpointed). > > Absolutely. Oren's code does it this way to make for a smaller patch at > first. The syscall takes a pid argument so it is surely expected to be > expanded upon later. > > > Also I think that all the restart job (including process forking) should > > be done in kernel, as in this case we will not depend on user space and > > will be more secure. This is also implemented in my patchset. > > Do you think that this is an approach that Oren's patches are married > to, or is this a "feature" we can add on later?
Well, AFAICS from Oren's patch set his approach is oriented on process creation in user space. I think we should choose right now what approach will be used for process creation. We have two options here: fork processes in kernel or fork them in user space. If process will be forked in user space, then there will be a gap when process will be in user space and can be killed with received signal before entering kernel. Also we will need a functionolity to create processes with predefined PID. I think it is not very good to provide such ability to user space. That is why we prefer in OpenVZ to do all the job in kernel.
> I don't care which patch set we end up sticking in the kernel. I'm > trying to figure out which code we can more easily build upon in the > future. The fact that Oren's or yours can't do certain little things > right now does not bother me. > > Honestly, I'm a little more confident that everyone can work with Oren > since he managed to get 7 revisions of his patch out and make some > pretty large changes while in the same time the OpenVZ patch was only > released twice. I'm not sure what has changed in the OpenVZ patch > between releases, either.
That is my fault. I am working right now on my Ph.D, that is why my activity is not very high. But now I hope I will have more time for that.
> Are there any reasons that you absolutely can not use the code Oren > posted? Will it not fulfill your needs somehow? If so, could you > please elaborate on how?
We have one major difference with Oren's code - how processes are created during restr. Right now I'm trying to port kernel process creation on top of Oren's patches. I agree that working in collaboration will speed up merging of checkpointing to mainstream.
Andrey
P.S.: Sorry for late reply, my mailer attached your e-mail to wrong thread.
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