QFQ_MIN_SLOT_SHIFT
size_map = (unsigned long)(slot_size >> QFQ_MIN_SLOT_SHIFT);
index -= !(slot_size - (1ULL << (index + QFQ_MIN_SLOT_SHIFT - 1)));
vslot = q->V >> QFQ_MIN_SLOT_SHIFT;
old_vslot = old_V >> QFQ_MIN_SLOT_SHIFT;