oom: use pte pages in OOM score

PTE pages eat up memory just like anything else, but we do not account for
them in any way in the OOM scores.  They are also _guaranteed_ to get
freed up when a process is OOM killed, while RSS is not.
Reported-by: NDave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Cc: <stable@kernel.org>		[2.6.36+]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/oom_kill.c

@@ -172,10 +172,13 @@ unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem,
 
 	/*
 	 * The baseline for the badness score is the proportion of RAM that each
-	 * task's rss and swap space use.
+	 * task's rss, pagetable and swap space use.
 	 */
-	points = (get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS)) * 1000 /
-			totalpages;
+	points = get_mm_rss(p->mm) + p->mm->nr_ptes;
+	points += get_mm_counter(p->mm, MM_SWAPENTS);
+
+	points *= 1000;
+	points /= totalpages;
 	task_unlock(p);
 
 	/*