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    SubjectRe: Active Memory Defragmentation: Our implementation & problems
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    On Wed, 2004-02-04 at 10:54, Alok Mooley wrote:
    > --- Dave Hansen <haveblue@us.ibm.com> wrote:
    >
    > > The "work until we get interrupted and restart if
    > > something changes
    > > state" approach is very, very common. Can you give
    > > some more examples
    > > of just how a page fault would ruin the defrag
    > > process?
    > >
    >
    > What I mean to say is that if we have identified some
    > pages for movement, & we get preempted, the pages
    > identified as movable may not remain movable any more
    > when we are rescheduled. We are left with the task of
    > identifying new movable pages.

    Depending on the quantity of work that you're trying to do at once, this
    might be unavoidable.

    I know it's a difficult thing to think about, but I still don't
    understand the precise cases that you're concerned about. Page faults
    to me seem like the least of your problems. A bigger issue would be if
    the page is written to by userspace after you copy, but before you
    install the new pte. Did I miss the code in your patch that invalidated
    the old tlb entries?

    --dave

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