oom: use pte pages in OOM score

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: Dave Hansen <[email protected]>
Signed-off-by: KOSAKI Motohiro <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Acked-by: David Rientjes <[email protected]>
Cc: <[email protected]>		[2.6.36+]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>