Messages in this thread | | | From | Daniel Phillips <> | Subject | Re: large page patch (fwd) (fwd) | Date | Fri, 9 Aug 2002 20:43:42 +0200 |
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On Friday 09 August 2002 20:32, Hubertus Franke wrote: > On Friday 09 August 2002 11:20 am, Daniel Phillips wrote: > > On Sunday 04 August 2002 19:19, Hubertus Franke wrote: > > > "General Purpose Operating System Support for Multiple Page Sizes" > > > htpp://www.usenix.org/publications/library/proceedings/usenix98/full_pape > > >rs/ganapathy/ganapathy.pdf > > > > This reference describes roughly what I had in mind for active > > defragmentation, which depends on reverse mapping. The main additional > > wrinkle I'd contemplated is introducing a new ZONE_LARGE, and GPF_LARGE, > > which means the caller promises not to pin the allocation unit for long > > periods and does not mind if the underlying physical page changes > > spontaneously. Defragmenting in this zone is straightforward. > > I think the objection to that is that in many cases the cost of > defragmentation is to heavy to be recollectable through TLB miss handling > alone.
You pay the cost only on transition from a load that doesn't use many large pages to one that does, it is not an ongoing cost.
> [...] > > Defragmenting to me seems a matter of last resort, Copying pages is expensive.
It is the only way to ever have a seamless implementation. Really, I don't understand this fear of active defragmentation. Oh well, like davem said, code talks.
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