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    SubjectRe: [RFC] Track mlock()ed pages
    On Fri, 26 Jan 2007 07:44:42 -0800 (PST)
    Christoph Lameter <clameter@sgi.com> wrote:

    > On Fri, 26 Jan 2007, Andrew Morton wrote:
    >
    > > > > > Track mlocked pages via a ZVC
    > >
    > > Why?
    >
    > Large amounts of mlocked pages may be a problem for
    >
    > 1. Reclaim behavior.
    >
    > 2. Defragmentation
    >

    We know that. What has that to do with this patch?

    >
    > > You could perhaps go for a walk across all the other vmas which presently
    > > map this page. If any of them have VM_LOCKED, don't increment the counter.
    > > Similar on removal: only decrement the counter when the final mlocked VMA
    > > is dropping the pte.
    >
    > For that we would need an additional refcount for vmlocked maps in the
    > page struct.

    No you don't. The refcount is already there. It is "the sum of the VM_LOCKED
    VMAs which map this page".

    It might be impractical or expensive to calculate it, but it's there.
    -
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