Re: [PATCH] oom: break after selecting process to kill

[Michal Hocko <mhocko@suse.cz>]

On Sun 14-09-14 13:46:15, David Rientjes wrote:
> On Fri, 12 Sep 2014, Niv Yehezkel wrote:
> 
> > > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> > > > index 1e11df8..3203578 100644
> > > > --- a/mm/oom_kill.c
> > > > +++ b/mm/oom_kill.c
> > > > @@ -315,7 +315,7 @@ static struct task_struct *select_bad_process(unsigned int *ppoints,
> > > >  		case OOM_SCAN_SELECT:
> > > >  			chosen = p;
> > > >  			chosen_points = ULONG_MAX;
> > > > -			/* fall through */
> > > > +			break;
> > > >  		case OOM_SCAN_CONTINUE:
> > > >  			continue;
> > > >  		case OOM_SCAN_ABORT:
> > > > @@ -324,6 +324,8 @@ static struct task_struct *select_bad_process(unsigned int *ppoints,
> > > >  		case OOM_SCAN_OK:
> > > >  			break;
> > > >  		};
> > > > +		if (chosen_points == ULONG_MAX)
> > > > +			break;
> > > >  		points = oom_badness(p, NULL, nodemask, totalpages);
> > > >  		if (!points || points < chosen_points)
> > > >  			continue;
> > > > -- 
> > > > 1.7.10.4
> > > > 
> > > 
> > > 
> > > -- 
> > > Michal Hocko
> > > SUSE Labs
> > 
> > As mentioned earlier, there's no need to keep iterating over all
> > running processes once the process with the highest score has been found.
> > 
> 
> This would lead to unnecessary oom killing since we may miss a process 
> that returns OOM_SCAN_ABORT simply because it is later in the tasklist (we 
> want to defer oom killing if there is an exiting process or an oom kill 
> victim hasn't exited yet).  NACK.

Good point David. I have completely missed this part!

-- 
Michal Hocko
SUSE Labs

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