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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2014-06-30 at 17:10 +0100, Julien Grall wrote:
> 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.

Inserting the new bank before, retaining the ordering.

Ian.


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