read_ctrl_pos
read_ctrl_pos(lruvec, type, 0, 2, &sp);
read_ctrl_pos(lruvec, type, tier, 3, &pv);
read_ctrl_pos(lruvec, LRU_GEN_ANON, MAX_NR_TIERS, swappiness, &sp);
read_ctrl_pos(lruvec, LRU_GEN_FILE, MAX_NR_TIERS, MAX_SWAPPINESS - swappiness, &pv);