Messages in this thread |  | | | Date | Thu, 12 May 2011 12:38:28 -0700 (PDT) | | From | David Rientjes <> | | Subject | Re: OOM Killer don't works at all if the system have >gigabytes memory (was Re: [PATCH] mm: check zone->all_unreclaimable in all_unreclaimable()) |
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On Thu, 12 May 2011, Minchan Kim wrote:
> > processes a 1% bonus for every 30% of memory they use as proposed > > earlier.) > > I didn't follow earlier your suggestion. > But it's not formal patch so I expect if you send formal patch to > merge, you would write down the rationale. >
Yes, I'm sure we'll still have additional discussion when KOSAKI-san replies to my review of his patchset, so this quick patch was written only for CAI's testing at this point.
In reference to the above, I think that giving root processes a 3% bonus at all times may be a bit aggressive. As mentioned before, I don't think that all root processes using 4% of memory and the remainder of system threads are using 1% should all be considered equal. At the same time, I do not believe that two threads using 50% of memory should be considered equal if one is root and one is not. So my idea was to discount 1% for every 30% of memory that a root process uses rather than a strict 3%.
That change can be debated and I think we'll probably settle on something more aggressive like 1% for every 10% of memory used since oom scores are only useful in comparison to other oom scores: in the above scenario where there are two threads, one by root and one not by root, using 50% of memory each, I think it would be legitimate to give the root task a 5% bonus so that it would only be selected if no other threads used more than 44% of memory (even though the root thread is truly using 50%).
This is a heuristic within the oom killer badness scoring that can always be debated back and forth, but I think a 1% bonus for root processes for every 10% of memory used is plausible.
Comments?
> > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > > --- a/mm/oom_kill.c > > +++ b/mm/oom_kill.c > > @@ -160,7 +160,7 @@ unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem, > > */ > > if (p->flags & PF_OOM_ORIGIN) { > > task_unlock(p); > > - return 1000; > > + return 10000; > > } > > > > /* > > @@ -177,32 +177,32 @@ unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem, > > points = get_mm_rss(p->mm) + p->mm->nr_ptes; > > points += get_mm_counter(p->mm, MM_SWAPENTS); > > > > - points *= 1000; > > + points *= 10000; > > points /= totalpages; > > task_unlock(p); > > > > /* > > - * Root processes get 3% bonus, just like the __vm_enough_memory() > > - * implementation used by LSMs. > > + * Root processes get 1% bonus per 30% memory used for a total of 3% > > + * possible just like LSMs. > > */ > > if (has_capability_noaudit(p, CAP_SYS_ADMIN)) > > - points -= 30; > > + points -= 100 * (points / 3000); > > > > /* > > * /proc/pid/oom_score_adj ranges from -1000 to +1000 such that it may > > * either completely disable oom killing or always prefer a certain > > * task. > > */ > > - points += p->signal->oom_score_adj; > > + points += p->signal->oom_score_adj * 10; > > > > /* > > * Never return 0 for an eligible task that may be killed since it's > > - * possible that no single user task uses more than 0.1% of memory and > > + * possible that no single user task uses more than 0.01% of memory and > > * no single admin tasks uses more than 3.0%. > > */ > > if (points <= 0) > > return 1; > > - return (points < 1000) ? points : 1000; > > + return (points < 10000) ? points : 10000; > > } > > > > /* > > @@ -314,7 +314,7 @@ static struct task_struct *select_bad_process(unsigned int *ppoints, > > */ > > if (p == current) { > > chosen = p; > > - *ppoints = 1000; > > + *ppoints = 10000; > > Scattering constant value isn't good. > You are proving it now. > I think you did it since this is not a formal patch. > I expect you will define new value (ex, OOM_INTERNAL_MAX_SCORE or whatever) >
Right, we could probably do something like
#define OOM_SCORE_MAX_FACTOR 10 #define OOM_SCORE_MAX (OOM_SCORE_ADJ_MAX * OOM_SCORE_MAX_FACTOR)
in mm/oom_kill.c, which would then be used to replace all of the constants above since OOM_SCORE_ADJ_MAX is already defined to be 1000 in include/linux/oom.h. |  |