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

[Matthew Rushton <mvrushton@xxxxxxxxx>]

On 04/09/14 23:14, Jan Beulich wrote:
> > > > On 10.04.14 at 00:21, <mvrushton@xxxxxxxxx> wrote:
> > On 04/02/14 03:20, Ian Campbell wrote:
> > > Dom0 ballooning breaks any assumptions you might make about relying on
> > > early allocations.
> > I think you're missing the point. I'm not arguing that this change is a
> > general purpose solution to guarantee that dom0 is contiguous.
> > Fragmentation can exist even if dom0 asks for larger allocations like it
> > should (which the balloon driver does I believe). What the change does
> > do is solve a real problem in the current Linux PCI remapping
> > implementation which happens during dom0 intialization. If the
> > allocation strategy is arbitrary why not make the proposed hypervisor
> > change to make existing Linux implementations behave better and in
> > addition fix the problem in Linux so moving forward things are safe?
> Apart from all other arguments speaking against this, did you
> consider that altering the hypervisor behavior may adversely
> affect some other Dom0-capable OS?
Sure I've been considering the more intuitive dom0 implementation of 
allocating memory low to high and looking at things pragmatically.
> Problems in Linux should, as said before, get fixed in Linux. If
> older versions are affected, stable backports should subsequently
> be requested/done.
>
> Jan

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