Re: Copy-on-write memory to allow many more xenU domains per machine

[David Hopwood <david.nospam.hopwood@blueyonder.co.uk>]

Ian Pratt wrote:
>>Hello
>>
>>Some time ago Michael Vrable talked about copy-on-write memory to enable 
>>large numbers of nearly identical machines to run on the same physical
>>hardware. Is this a feasible proposition? I asked a few days ago in the 
>>original thread, but no-one seems to have noticed. It seems to me that 
>>it would be a very significant feature to offer.
> 
> It's useful for honeypots and other situations where you want
> very large numbers of VMs, but isn't generally a huge win.
> 
> When I was doing the live migration work I recorded fingerprints
> of all VM pages that were on several systems, and didn't find a
> whole lot of commonality between VMs.

I thought the idea would be to have a 'clone' primitive that would work
in a similar way to Unix fork? The clone would start off sharing all
pages, although a lot of them would get copied fairly quickly. Does
anyone have an idea of what proportion or number of pages in a Linux
system stay constant (and are not paged out) after boot?

-- 
David Hopwood <david.nospam.hopwood@blueyonder.co.uk>



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