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    SubjectRe: [PATCH 0/4] exit: Make unlikely case in mm_update_next_owner() more scalable
    On Thu 26-04-18 14:00:19, Kirill Tkhai wrote:
    > This function searches for a new mm owner in children and siblings,
    > and then iterates over all processes in the system in unlikely case.
    > Despite the case is unlikely, its probability growths with the number
    > of processes in the system. The time, spent on iterations, also growths.
    > I regulary observe mm_update_next_owner() in crash dumps (not related
    > to this function) of the nodes with many processes (20K+), so it looks
    > like it's not so unlikely case.

    Did you manage to find the pattern that forces mm_update_next_owner to
    slow paths? This really shouldn't trigger very often. If we can fallback
    easily then I suspect that we should be better off reconsidering
    mm->owner and try to come up with something more clever. I've had a
    patch to remove owner few years back. It needed some work to finish but
    maybe that would be a better than try to make non-scalable thing suck
    less.

    --
    Michal Hocko
    SUSE Labs

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