linux-kernel - Re: OOM Killer don't works at all if the system have >gigabytes memory (was Re: [PATCH] mm: check zone->all_unreclaimable in all

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Date:	Wed, 11 May 2011 13:34:01 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	CAI Qian <caiqian@...hat.com>
cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>, avagin@...il.com,
	Andrey Vagin <avagin@...nvz.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Minchan Kim <minchan.kim@...il.com>,
	Hugh Dickins <hughd@...gle.com>,
	Oleg Nesterov <oleg@...hat.com>
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())

On Tue, 10 May 2011, CAI Qian wrote:

> Sure, I saw there were some discussion going on between you and David
> about your patches. Does it make more sense for me to test those after
> you have settled down technical arguments?
> 

Something like the following (untested) patch should fix the issue by 
simply increasing the range of a task's badness from 0-1000 to 0-10000.

There are other things to fix like the tasklist dump output and 
documentation, but this shows how easy it is to increase the resolution of 
the scoring.  (This patch also includes a change to only give root 
processes a 1% bonus for every 30% of memory they use as proposed 
earlier.)


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;
 			} else {
 				/*
 				 * If this task is not being ptraced on exit,
--
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