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    SubjectRe: [2.4] heavy-load under swap space shortage
    On Wed, 26 May 2004, Marcelo Tosatti wrote:

    > Andrea, Hugh, Jun'ichi,
    >
    > I think we can merge this patch.

    I guess so. I'm unenthusiastic since I've never worked out whether
    it's _right_, or just an ad hoc hack that happens to work around
    more fundamental issues, quite successfully in some workloads.

    Andrea seems to have devised it to reduce pagemap_lru_lock
    contention on bigiron, yet here it's solving a different problem.
    Which may be a sign that it's a great patch, or a sign that we
    (I!) don't understand what goes on here well enough.

    Please don't count me as against it: I just don't know.

    (My involvement was earlier when Jun'ichi reported page_table_lock
    contention there. We were working together on an entirely different
    kind of patch addressing that issue, when Andrea suggested he try this
    vm_anon_lru patch. As I understand it, that solved Jun'ichi's particular
    problem much more satisfactorily than our own dabblings; but I rather
    dropped out at that point.)

    > Its very safe - default behaviour unchanged.

    Yes, but please update the comments to reflect that, they imply
    vm_anon_lru 0 by default, presumably how it was in Andrea's tree.

    The tunability, of course, does unfairly make it look more like a
    hack than it is; but if we're uncertain, yes, a tunable hack is
    much better than a wrong decision now.

    Hugh

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