On Fri 26-08-11 11:53:56, Michal Hocko wrote: > On Fri 26-08-11 02:21:42, David Rientjes wrote: > > On Fri, 26 Aug 2011, Michal Hocko wrote: > > > > > Let's give all frozen tasks a bonus (OOM_SCORE_ADJ_MAX/2) so that we do > > > not consider them unless really necessary and if we really pick up one > > > then thaw its threads before we try to kill it. > > > > > > > I don't like arbitrary heuristics like this because they polluted the old > > oom killer before it was rewritten and made it much more unpredictable. > > The only heuristic it includes right now is a bonus for root tasks so that > > when two processes have nearly the same amount of memory usage (within 3% > > of available memory), the non-root task is chosen instead. > > > > This bonus is actually saying that a single frozen task can use up to 50% > > more of the machine's capacity in a system-wide oom condition than the > > task that will now be killed instead. That seems excessive. > > Yes, the number is probably too high. I just wanted to start up with > something. Maybe we can give it another root bonus. But I agree whatever > we use it will be just a random value... > > > > > I do like the idea of automatically thawing the task though and if that's > > possible then I don't think we need to manipulate the badness heuristic at > > all. I know that wouldn't be feasible when we've frozen _all_ threads and > > Why it wouldn't be feasible for all threads? If you have all tasks > frozen (suspend going on, whole cgroup or all tasks in a cpuset/nodemask > are frozen) then the selection is more natural because all of them are > equal (with or without a bonus). The bonus tries to reduce thawing if > not all of them are frozen. > I am not saying the bonus is necessary, though. It depends on what > the freezer is used for (e.g. freeze a process which went wild and > debug what went wrong wouldn't welcome that somebody killed it or other > (mis)use which relies on D state). Anyway, I do agree, the two things (bonus and thaw during oom_kill) should be handled separately. -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>