Messages in this thread | | | Date | Tue, 09 Mar 2004 18:23:53 +1100 | From | Nick Piggin <> | Subject | Re: [RFC][PATCH 4/4] vm-mapped-x-active-lists |
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William Lee Irwin III wrote:
>On Tue, Mar 09, 2004 at 05:06:37PM +1100, Nick Piggin wrote: > >>Not sure to be honest, I haven't looked at it :\. I'm not really >>sure if the rmap mitigation direction is just a holdover until >>page clustering or intended as a permanent feature... >>Either way, I trust its proponents will take the onus for regressions. >> > >Actually, anobjrmap does wonderful things wrt. liberating pgcl >internals from some very frustrating complications having to do with >assumptions of a 1:1 correspondence between pte pages and struct pages, >so I would regard work in the direction of anobjrmap as useful to >advance the state of page clustering regardless of its rmap mitigation >overtones. The "partial" objrmap is actually insufficient to clean up >this assumption, and introduces new failure modes I don't like (which >it is in fact not necessary to do; aa's code is very close to doing the >partial-but-insufficient-for-pgcl objrmap properly apart from trying to >allocate more pte_chains than necessary and not falling back to the vma >lists for linear/nonlinear mapping mixtures). The current port has some >code to deal with this I'm extremely eager to dump as soon as things >such as anobjrmap etc. make it possible, if they're merged. > >Current efforts are now a background/spare time affair centering around >non-i386 architectures and driver audits. >
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?
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