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    SubjectRe: page fault scalability patch V11 [0/7]: overview
    On Fri, Nov 19, 2004 at 11:59:03AM -0800, Linus Torvalds wrote:
    > You could also make "rss" be a _signed_ integer per-thread.
    > When unmapping a page, you decrement one of the threads that shares the mm
    > (doesn't matter which - which is why the per-thread rss may go negative),
    > and when mapping a page you increment it.
    > Then, anybody who actually wants a global rss can just iterate over
    > threads and add it all up. If you do it under the mmap_sem, it's stable,
    > and if you do it outside the mmap_sem it's imprecise but stable in the
    > long term (ie errors never _accumulate_, like the non-atomic case will
    > do).
    > Does anybody care enough? Maybe, maybe not. It certainly sounds a hell of
    > a lot better than the periodic scan.

    Unprivileged triggers for full-tasklist scans are NMI oops material.


    -- wli
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