Re: [Xen-devel] [RFC PATCH] page_alloc: use first half of higher order chunks when halving

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Mon, Apr 14, 2014 at 04:34:47PM +0100, Jan Beulich wrote:
> >>> On 14.04.14 at 16:40, <konrad.wilk@xxxxxxxxxx> wrote:
> > That was OK, but the M2P lookup table was not too thrilled with this.
> > Perhaps I should have used another hypercall to re-arrange the M2P?
> > I think I did try 'XENMEM_exchange' but that is not the right call either.
> 
> Yeah, that's allocating new pages in exchange for your old ones. Not
> really what you want.
> 
> > Perhaps I should use XENMEM_remove_from_physmap/XENMEM_add_to_physmap
> > combo ?
> 
> A pair of MMU_MACHPHYS_UPDATE operations would seem to be the
> right way of doing this (along with respective kernel internal accounting
> like set_phys_to_machine(), and perhaps a pair of update_va_mapping
> operations if the 1:1 map is already in place at that time, and you care
> about which page contents appears at which virtual address).

OK.

Matt & Matthew - my plate is quite filled and I fear that in the next three
weeks there is not going to be much time to code up a prototype.

Would either one of you be willing to take a crack at this? It would
be neat as we could remove a lot of the balloon increase/decrease code
in arch/x86/xen/setup.c.

Thanks!
> 
> Jan
> 

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