Re: [RFC][PATCH] oom_kill: avoid depends on total_vm and use realRSS/swap value for oom_score (Re: Memory overcommit

[KAMEZAWA Hiroyuki]

On Tue, 27 Oct 2009 17:52:43 +0900
Minchan Kim <minchan.kim@xxxxxxxxx> wrote:

> On Tue, 27 Oct 2009 17:33:08 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> 
> > On Tue, 27 Oct 2009 17:14:41 +0900
> > Minchan Kim <minchan.kim@xxxxxxxxx> wrote:
> > 
> > > On Tue, 27 Oct 2009 16:56:28 +0900
> > > KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> > > 
> > > > On Tue, 27 Oct 2009 16:45:26 +0900
> > > > KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> > > >   	/*
> > > > >  	 * After this unlock we can no longer dereference local variable `mm'
> > > > > @@ -92,8 +93,13 @@ unsigned long badness(struct task_struct
> > > > >  	 */
> > > > >  	list_for_each_entry(child, &p->children, sibling) {
> > > > >  		task_lock(child);
> > > > > -		if (child->mm != mm && child->mm)
> > > > > -			points += child->mm->total_vm/2 + 1;
> > > > > +		if (child->mm != mm && child->mm) {
> > > > > +			unsigned long cpoint;
> > > > > +			/* At considering child, we don't count swap */
> > > > > +			cpoint = get_mm_counter(child->mm, anon_rss) +
> > > > > +				 get_mm_counter(child->mm, file_rss);
> > > > > +			points += cpoint/2 + 1;
> > > > > +		}
> > > > >  		task_unlock(child);
> > > > 
> > > > BTW, I'd like to get rid of this code.
> > > > 
> > > > Can't we use other techniques for detecting fork-bomb ?
> > > > 
> > > > This check can't catch following type, anyway.
> > > > 
> > > >    fork()
> > > >      -> fork()
> > > >           -> fork()
> > > >                -> fork()
> > > >                     ....
> > > > 
> > > > but I have no good idea.
> > > > What is the difference with task-launcher and fork bomb()...
> > > > 
> > > 
> > > I think it's good as-is. 
> > > Kernel is hard to know it by effiecient method.
> > > It depends on applications. so Doesnt's task-launcher 
> > > like gnome-session have to control his oom_score? 
> > > 
> > > Welcome to any ideas if kernel can do it well.
> > > 
> > Hmmm, check system-wide fork/sec and fork-depth ? Maybe not difficult to calculate..
> 
> Yes. We can do anything to achieve the goal in kernel. 
> Maybe check the time or fork-depth counting. 
> What I have a concern is how we can do it nicely if it is a serious
> problem in kernel. ;)
> 
yes...only the user knows whether user is wrong, finally. Especially in case
of memory leak.

> I think most of program which have many child are victims of OOM killing.
> It make sense to me. There is some cases to not make sense like task-launcher.
> So I think if task-launcher which is very rare and special program can change
> oom_adj by itself, it's good than thing that add new heuristic in kernel.
> 
> It's just my opinon. :)
> 
I know KDE already adjsut oom_adj for their 3.5 release ;)
Okay, concentrate on avoiding total_vm issue for a while.

Thanks,
-Kame


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