Re: [patch 0/6] Guest page hinting version 7.

[Jeremy Fitzhardinge]

Rik van Riel wrote:
> Jeremy Fitzhardinge wrote:
>
> > That said, people have been looking at tracking block IO to work out 
> > when it might be useful to try and share pages between guests under Xen.
>
> Tracking block IO seems like a bass-ackwards way to figure
> out what the contents of a memory page are.

Well, they're research projects, so nobody said that they're necessarily 
useful results ;).  I think the rationale is that, in general, there 
aren't all that many sharable pages, and asize from zero-pages, the bulk 
of them are the result of IO.  Since its much simpler to compare 
device+block references than doing page content matching, it is worth 
looking at the IO stream to work out what your candidates are.

> The KVM KSM code has a simpler, yet still efficient, way of
> figuring out which memory pages can be shared.
How's that?  Does it do page content comparison?

   J

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