Re: [Xen-devel] [PATCH] xen/arm: skip first page when RAM starts at 0x0

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.04.19 at 17:54, <julien.grall@xxxxxxx> wrote:
> Anyway, I also tested the change suggested by Stefano. This will 
> substantially 
> increase the size of the frametable on platform where the RAM does not start 
> at 0.
> 
> For instance, on Foundation Model the RAM starts at 2GB. As we don't compress 
> any of the first 31 bits, the frametable will now be 28MB bigger than we 
> currently have (112MB up from 84MB).
> 
> So I think what we want is:
> 
> nr_pdxs = pfn_to_pdx(end - 1) - pfn_to_pdx(start) + 1;
> frame_table_base_pdx = pfn_to_pdx(start);

Yes, if there's only a single memory range at 2Gb, then subtracting
the base address will of course yield better results. But if there are
multiple regions, things really depend on the placement of all of
them.

Jan



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