Re: [PATCH 0/4] exit: Make unlikely case in mm_update_next_owner() more scalable

[Michal Hocko]

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