Fix several oom killer bugs, most important avoid spurious oom kills
badness algorithm tweaked by Thomas Gleixner to deal with fork bombs

This is the core of the oom-killer fixes I developed partly taking
the idea from Thomas's patches of getting feedback from the exit
path, plus I moved the oom killer into page_alloc.c as it should to
be able to check the watermarks before killing more stuff.  This
also tweaks the badness to take thread bombs more into account (that
change to badness is from Thomas, from my part I'd rather rewrite
badness from scratch instead, but that's an orthgonal issue ;).
With this applied the oom killer is very sane, no more 5 sec waits
and suprious oom kills.
Signed-off-by: Andrea Arcangeli <andrea@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>