Messages in this thread | | | Subject | Re: [PATCH] Tight check of pfn_valid on sparsemem - v4 | From | Dave Hansen <> | Date | Fri, 30 Jul 2010 08:43:54 -0700 |
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On Fri, 2010-07-30 at 07:48 -0500, Christoph Lameter wrote: > On Thu, 29 Jul 2010, Dave Hansen wrote: > > > SPARSEMEM_EXTREME would be a bit different. It's a 2-level lookup. > > You'd have 16 "section roots", each representing 256MB of address space. > > Each time we put memory under one of those roots, we'd fill in a > > 512-section second-level table, which is designed to always fit into one > > page. If you start at 256MB, you won't waste all those entries. > > That is certain a solution to the !MMU case and it would work very much > like a page table. If you have an MMU then the vmemmap sparsemem > configuration can take advantage of of that to avoid the 2 level lookup.
Yup, couldn't agree more, Christoph.
It wouldn't hurt to have several them available on ARM since the architecture is so diverse.
-- Dave
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