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    SubjectRe: PROBLEM: Linux 2.6.0-test11 only lets me use 1GB out of 2GB ram.
    On Wed, Dec 10, 2003 at 09:41:11PM -0800, William Lee Irwin III wrote:
    >> You're probably thinking of 2:2 split patches.
    >> 2:2 splits are at least technically ABI violations, which is probably
    >> why this isn't merged etc. Applications sensitive to it are uncommon.
    >> Yes, the SVR4 i386 ELF/ABI spec literally mandates 0xC0000000 as the
    >> top of the process address space.

    On Thu, Dec 11, 2003 at 09:41:48AM -0500, Raul Miller wrote:
    > Apologies if I'm asking about the obvious, but...
    > [1] isn't 0xC0000000 at 3GB?

    It is.


    On Thu, Dec 11, 2003 at 09:41:48AM -0500, Raul Miller wrote:
    > [2] Even if ELF did restrict a user process to 1GB (which I'm pretty
    > sure it doesn't), wouldn't the kernel still be able to manage 2GB of
    > user memory?

    You have it backward. The SVR4/i386 ELF ABI specification is requiring
    userspace to be granted at least 3GB of address space.

    This does not necessarily present a restriction for the kernel;
    consider task gates (mingo did it by hand).


    On Thu, Dec 11, 2003 at 09:41:48AM -0500, Raul Miller wrote:
    > Probably my real question is: "what's this about 2:2 split patches"?
    > Basically, I thought "linux supports 2GB ram" had been been the case
    > since the dark ages. It's hard for me to comprehend how highmem, or 64
    > bit cpus, could have much to do with a 1GB limit.

    You should probably ignore this thread. It's probably not relevant to
    you.


    On Thu, Dec 11, 2003 at 09:41:48AM -0500, Raul Miller wrote:
    > [In my fantasies, I was thinking that the system came up with only 1GB of
    > the memory easily usable, and that the lack of support for my hardware
    > meant that it couldn't be properly reconfigured. But I recognize that
    > I haven't spent the time researching this to see if in fact this is
    > the case.]

    Highmem support gets you this on ia32. Other architectures can support it
    with less overhead.


    On Thu, Dec 11, 2003 at 09:41:48AM -0500, Raul Miller wrote:
    > I am in the process of bringing up an cross compilation environment for
    > amd64 -- I need to do that anyways -- and I'll try building a real 64
    > bit kernel to see if that helps any. If that doesn't, I guess I'll try
    > a couple 4G highmem kernels (one 64 bit, one 32 bit). If nothing else,
    > that will eat up some time...

    If you have such a cpu why are you bothering with highmem (or wondering
    if > 2GB is supported)?


    -- wli
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