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    SubjectRe: [RFC 2.6.11-rc2-mm2 7/7] mm: manual page migration -- sys_page_migrate
    On Mon, Feb 14, 2005 at 10:50:42AM -0800, Dave Hansen wrote:
    > On Mon, 2005-02-14 at 07:52 -0600, Robin Holt wrote:
    > > The node mask is a list of allowed. This is intended to be as near
    > > to a one-to-one migration path as possible.
    >
    > If that's the case, it would make the kernel internals a bit simpler to
    > only take a "from" and "to" node, instead of those maps. You'll end up
    > making multiple syscalls, but that shouldn't be a problem.

    Then how do you handle overlapping nodes. If I am doing a 5->4, 4->3,
    3->2, 2->1 shift in the memory placement and had only a from and to node,
    I would end up calling multiple times. This would end up in memory shifting
    from 5->4 on the first, 4->3 on the second, ... with the end result of
    all memory shifting to a single node.

    With the array-of-node maps, you make a single pass across the address
    space. This results in a clean mapping without the userspace needing to
    know which nodes the pages are on.

    On a seperate topic, I would guess the syscall time is trivial compared
    to the time to walk the page tables.

    Thanks,
    Robin
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