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Re: [Xen-devel] Cloning a VM and copy-on-write deduplicating memory using CoW page sharing in Xen 4+

  • To: "Patrick Wilbur" <patrick.wilbur@xxxxxxxxx>
  • From: "Andres Lagar-Cavilla" <andres@xxxxxxxxxxxxxxxx>
  • Date: Thu, 2 Feb 2012 11:23:47 -0800
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Thu, 02 Feb 2012 19:24:28 +0000
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  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

> Hey all,
> Hey Andres,
> I'm looking to clone a VM into several extremely-similar VMs, and I'm
> hoping to also make use of your lovely new CoW page sharing capabilities
> in
> Xen 4.
> From my understanding of a previous thread where Andres described the
> process of sharing/coalescing memory between VMs, it sounds like I will
> need to "manually" coalesce each page using a homebrew tool of mine.  The
> issue I have with doing this is it seems like I'd need to pause, save mem,
> load mem in a new VM, coalesce, and resume two VMs, which seems painful
> and
> wasteful of a process for cloning!

that is indeed painful and wasteful. That is why we added
xc_memshr_add_to_physmap. Now you can do Potemkin-/SnowFlock-like cloning
in a few lines of code. You still want the source VM to be paused,

Yuengling is my favourite US beer ;)


> Is there an easier way to do this, or should we add a new feature for CoW
> cloning of VMs in Xen via a userspace tool?
> Thanks,
> Pat Wilbur & team
> --
> Patrick F. Wilbur
> Researcher, Consultant, Educator,
> Computer Science Graduate at Clarkson University
> DONE RIGHT THE FIRST TIME: Consulting and hiring information:
> http://pdub.net/consulting/ & http://pdub.net/hiring/
> patrick.wilbur@xxxxxxxxx
> wilburpf@xxxxxxxxxxxx
> Check out our book: http://runningxen.com
> My website: http://pdub.net

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