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    SubjectRe: Bug: Discontigmem virt_to_page() [Alpha,ARM,Mips64?]
    On Monday 06 May 2002 10:54, Roman Zippel wrote:
    > Hi,
    > On Mon, 6 May 2002, Daniel Phillips wrote:
    > > I must be guilty of not explaining clearly. Suppose you have the following
    > > physical memory map:
    > >
    > > 0: 128 MB
    > > 8000,0000: 128 MB
    > > 1,0000,0000: 128 MB
    > > 1,8000,0000: 128 MB
    > > 2,0000,0000: 128 MB
    > > 2,8000,0000: 128 MB
    > > 3,0000,0000: 128 MB
    > > 3,8000,0000: 128 MB
    > >
    > > The total is 1 GB of installed ram. Yet the kernel's 1G virtual space,
    > > can only handle 128 MB of it. The rest falls out of the addressable range and
    > > has to be handled as highmem, that is if you preserve the linear relationship
    > > between kernel virtual memory and physical memory, as config_discontigmem does.
    > > Even if you go to 2G of kernel memory (restricting user space to 2G of virtual)
    > > you can only handle 256 MB.
    > Why do you want to preserve the linear relationship between virtual and
    > physical memory?

    I don't, I observed that in all known instances of config_discontigmem, that
    linear relationship is preserved. Now, you and Andrea are suggesting that no
    such linear relation is strictly necessary and I believe its worth investigating
    further, to see how it would work and how it compares to config_nonlinear.

    > There is little common code (and only during
    > initialization), which assumes a direct mapping. I can send you the
    > patches to fix this.

    I already have patches to do that, that is, config_nonlinear. I'm interested in
    looking at your patches though, because we might as well give all the different
    approaches a fair examination.

    > Then you can map as much physical memory as you want
    > into a single virtual area and you only need a single pgdat.

    You're talking about your 68K solution with the loops that search through
    memory regions? If so, I've already looked at it and understand it. Or, if
    it's a new approach, then naturally I'd be interested.

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