[Xen-devel] Re: Memory fragmentation, order>0 allocation, and 4.0 dynamic RAM optimization features

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 19:11 +0000 on 08 Feb (1265656284), Keir Fraser wrote:
> I think everything but the shadow use of order-2 allocations is pretty easy
> to fix; just a case of logically carving up the multi-page structures.
> 
> I'm not sure, but suspect that fragmenting the shadow allocations may
> require extra book-keeping space in the page_info structure, for example.

I think it can be done without expanding page_info, but it involves
pretty invasive changes to all the parts of the shadow code that deal
with guest<->shadow mappings and with iterating across shadows.

As I said in response to an earlier email, I think the right thing to do
here is to move pretty much all allocation in Xen to superpage
granularity (and not just because it makes this issue go away!).

Tim

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, XenServer Engineering
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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