[Xen-devel] Re: Hugepage support to tmem.

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 11:10 +0000 on 25 Jan (1295953836), ashwin wasani wrote:
> Hi,
>     Can we modify the PS bit of PDE using structure page_info ?

Please don't top-post; it makes it harder to follow the thread of
conversation. 

No, you can't change any pagetable bits using struct page_info.  The
page_info structures correspond to physical/machine addresses, and
pagetables to virtual addresses.

Tim.

> On Mon, Oct 25, 2010 at 2:37 PM, Tim Deegan 
> <Tim.Deegan@xxxxxxxxxx<mailto:Tim.Deegan@xxxxxxxxxx>> wrote:
> Hi,
> 
> At 01:51 +0100 on 25 Oct (1287971515), Dan Magenheimer wrote:
> > > I think that in design consideration we need to solve this problem of
> > > splitting.
> > >
> > > According to code such splitting is done in HAP, so what exactly
> > > happens in shadow mode?
> >
> > I think Tim Deegan is much more of an expert in this area than
> > I am.  I have cc'ed him.
> 
> Shadow mode always uses 4k mappings for everything.  It should be
> possible to update it to use 2M mappings when the underlying memory is
> both contiguous and all the same type, but it would take a bit of
> cunning to do it without making refcounting very expensive.
> 
> HAP uses 2M mappings when it can - even the PoD code tries not to
> fragment into 4k mappings.  But if you're running PoD you're also using
> balloon drivers, and they always operate in 4K pages.  AFAIK, all
> existing balloon drivers will tend to fragment memory.
> 
> Cheers,
> 
> Tim.
> 
> --
> Tim Deegan <Tim.Deegan@xxxxxxxxxx<mailto:Tim.Deegan@xxxxxxxxxx>>
> Principal Software Engineer, XenServer Engineering
> Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)
> 
> 
> 
> --
> With Regards,
> Ashwin Vasani
> B.E. (Fourth Year)
> Computer  Engineering,
> Pune Institute of Computer Technology.
> +91 9960405802

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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