[vbox-dev] Pagefusion status

Klaus Espenlaub klaus.espenlaub at oracle.com
Wed Oct 26 13:02:35 UTC 2016

Hi Rob,

On 25.10.2016 09:25, Rob wrote:
> Hi Folks,
> The VirtualBox document mentioned:
> "VirtualBox supports Page Fusion only on 64-bit hosts, and it is not
> supported on Mac OS X hosts. Page Fusion currently works only with
> Windows guests (2000 and later)."
> I'd like to know is this still the latest state? PageFusion still can't
> work with Linux Guest?

Yes, the documentation is correct.

> If yes, do you have any plan to support PageFusion for Linux guest(which
> is widely used!).

Right now there's no short term plan to work on this. If there were 
plausible customer demand it would trigger re-evaluation of priorities 
based on the expected impact.

In which context are you interested in having PageFusion for Linux? Can 
you give an outline of the workload you have in mind and the memory 
savings you're expecting?

Oh, and a piece of advice: don't believe what some people out there 
publish in white papers. The savings they declare possible are often 
extremely unrealistic.

> Or any headlines if people want to try themselves?

Fundamentally it's possible to implement this in a similar fashion to 
the implementation for Windows - go over all readonly memory mapped 
files, declaring the corresponding memory regions as candidates.


> AFAIK, in order to make PageFusion work for Linux guest.
> There should be "HPVDEVSHAREDREGIONDESC regions" and then
> call VbglR3RegisterSharedModule() to register these regions.
> But I'm not sure is there any restrict in VbglR3RegisterSharedModule()
> for Linux Guest.
> Regards,
> Rob

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