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

[Matthew Rushton <mvrushton@xxxxxxxxx>]

On 04/16/14 07:15, Konrad Rzeszutek Wilk wrote:
> 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!
I have a first pass at this. Just need to test it and should have 
something ready sometime next week or so.
> > Jan

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