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    SubjectRe: large page patch (fwd) (fwd)
    Date
    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.

    --
    Daniel
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