linux-kernel - Re: [RFC] oom-kill: give the dying task a higher priority

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Date:	Wed, 2 Jun 2010 11:20:18 -0300
From:	"Luis Claudio R. Goncalves" <lclaudio@...g.org>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	David Rientjes <rientjes@...gle.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Minchan Kim <minchan.kim@...il.com>, balbir@...ux.vnet.ibm.com,
	Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Mel Gorman <mel@....ul.ie>, williams@...hat.com
Subject: Re: [RFC] oom-kill: give the dying task a higher priority

On Wed, Jun 02, 2010 at 10:54:01PM +0900, KOSAKI Motohiro wrote:
| > > @@ -291,9 +309,10 @@ static struct task_struct *select_bad_process(unsigned long *ppoints,
| > >  		 * Otherwise we could get an easy OOM deadlock.
| > >  		 */
| > >  		if (p->flags & PF_EXITING) {
| > > -			if (p != current)
| > > +			if (p != current) {
| > > +				boost_dying_task_prio(p, mem);
| > >  				return ERR_PTR(-1UL);
| > > -
| > > +			}
| > >  			chosen = p;
| > >  			*ppoints = ULONG_MAX;
| > >  		}
| > 
| > This has the potential to actually make it harder to free memory if p is 
| > waiting to acquire a writelock on mm->mmap_sem in the exit path while the 
| > thread holding mm->mmap_sem is trying to run.
| 
| if p is waiting, changing prio have no effect. It continue tol wait to release mmap_sem.

Ok, that was not a good idea after all :)

But I understand the !rt_task(p) test is necessary to avoid decrementing
the priority of an eventual RT task selected to die. Though it may also be
a corner case in badness().

Luis
-- 
[ Luis Claudio R. Goncalves                    Bass - Gospel - RT ]
[ Fingerprint: 4FDD B8C4 3C59 34BD 8BE9  2696 7203 D980 A448 C8F8 ]

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