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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.04.14 at 12:06, <Ian.Campbell@xxxxxxxxxx> wrote:
> On Wed, 2014-04-02 at 08:52 +0100, Jan Beulich wrote:
>> >>> On 02.04.14 at 02:17, <mvrushton@xxxxxxxxx> wrote:
>> > On 04/01/14 05:22, Tim Deegan wrote:
>> >> As long as we don't also change the default allocation order in
>> >> Xen. :)  In general, linux shouldn't rely on the order that Xen
>> >> allocates memory, as that might change later.  If the current API
>> >> can't do what's needed, maybe we can add another allocator
>> >> hypercall or flag?
>> > 
>> > Agree on not relying on the order in the long run. A new hypercall or 
>> > flag seems like overkill right now. The question for me comes down to my 
>> > proposed change which is more simple and solves the short term problem 
>> > or investing time in reworking the Linux code to make large allocations.
>> 
>> I think it has become pretty clear by now that we'd rather not alter
>> the hypervisor allocator for a purpose like this.
> 
> Does it even actually solve the problem? It seems like it is just
> deferring it until sufficient fragmentation has occurred in the system.
> All its really done is make the eventual issue much harder to debug.

Wasn't this largely for Dom0 (in which case fragmentation shouldn't
matter yet)?

Jan


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