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

[Matthew Rushton <mvrushton@gmail.com>]

On 04/09/14 23:14, Jan Beulich wrote:
>>>> On 10.04.14 at 00:21, <mvrushton@gmail.com> 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
>