Re: [PATCH v3 8/8] xen: arm: allocate more than one bank for 1:1 domain 0 if needed

[Julien Grall <julien.grall@linaro.org>]

Hi Ian,

On 06/30/2014 04:58 PM, Ian Campbell wrote:
> On Fri, 2014-06-27 at 14:09 +0100, Ian Campbell wrote:
>> On Fri, 2014-06-27 at 14:04 +0100, Julien Grall wrote:
>>>
>>> On 27/06/14 14:01, Ian Campbell wrote:
>>>>> Futhermore, it looks like we always allocate memory from the top of this
>>>>> zone. Is it normal?
>>>>
>>>> Normal behaviour is to allocate from as high as possible so I'm not
>>>> surprised that applies with a zone as well.
>>>
>>> For DOM0 bank allocation, shouldn't we try to allocate as lower as 
>>> possible? If not, we may not be able to create a second bank for dom0.
>>
>> The loop over bits is supposed to help there, but it's not as effective
>> with higher addresses I suppose.
>>
>> We'd need a new flag fore the allocate. Which is doable I guess. I'll
>> give it a try.
> 
> It's a bit tricky and involves messing with the guts of the page
> allocator, which I'd rather avoid...
> 
> We do allow allocations to be merged onto the start of bank 0, which in
> the normal case is what I would expect to happen, although it isn't
> guaranteed. In that case we would try higher addresses and might find
> enough RAM there.
> 
> I suppose I could relax the constraint a bit and allow new banks in
> front of bank zero if they were >= 128MB (say).

So, replacing the bank zero by the new bank, right? IIRC, some Linux
version are requiring the bank to be ordered.

Regards,

-- 
Julien Grall