Re: [RFC][PATCH 4/4] vm-mapped-x-active-lists

[William Lee Irwin III]

William Lee Irwin III wrote:
>> Current efforts are now a background/spare time affair centering around
>> non-i386 architectures and driver audits.

On Tue, Mar 09, 2004 at 06:23:53PM +1100, Nick Piggin wrote:
> OK. I had just noticed that the people complaining about rmap most
> are the ones using 4K page size (x86-64 uses 4K, doesn't it?). Not
> that this fact means it is OK to ignore them problem, but I thought
> maybe pgcl might solve it in a more general way.
> I wonder how much you gain with objrmap / anobjrmap on say a 64K page
> architecture?

pgcl doesn't reduce userspace's mapping granularity. The current
implementation has the same pte_chain overhead as mainline for the same
virtualspace mapped. It's unclear how feasible it is to reduce this
overhead, though various proposals have gone around. I've ignored the
potential pte_chain reduction issue entirely in favor of concentrating
on more basic correctness and functionality. The removal of the 1:1 pte
page : struct page assumption is the vastly more important aspect of
anobjrmap in relation to pgcl, since removing that assumption would
remove a significant piece of complexity.

-- wli
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