Re: How much of a mess does OpenVZ make? ;) Was: What can OpenVZ do?

On Fri, Feb 27, 2009 at 10:19:09AM +0100, Greg Kurz wrote:

On Fri, 2009-02-27 at 01:17 +0300, Alexey Dobriyan wrote:

quoted

On Thu, Feb 26, 2009 at 07:30:16PM +0100, Greg Kurz wrote:

quoted

On Thu, 2009-02-26 at 18:33 +0100, Ingo Molnar wrote:

quoted

I think the main question is: will we ever find ourselves in the 
future saying that "C/R sucks, nobody but a small minority uses 
it, wish we had never merged it"? I think the likelyhood of that 
is very low. I think the current OpenVZ stuff already looks very 

We've been maintaining for some years now a C/R middleware with only a
few hooks in the kernel. Our strategy is to leverage existing kernel
paths as they do most of the work right.

Most of the checkpoint is performed from userspace, using regular
syscalls in a signal handler or /proc parsing. Restart is a bit trickier
and needs some kernel support to bypass syscall checks and enforce a
specific id for a resource. At the end, we support C/R and live
migration of networking apps (websphere application server for example).

quoted

From our experience, we can tell:

Pros: mostly not-so-tricky userland code, independent from kernel
internals
Cons: sub-optimal for some resources

How do you restore struct task_struct::did_exec ?

With sys_execve().

How do you restore set of uts_namespace's? Kernel never exposes to
userspace which are the same, which are independent.
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