code: private void onMainHit(Node node) {
      node.remove();
      sizeMainQ[node.level]--;
      if (node.level < (levels - 1)) {
        node.level++;
      }
  
      Node head = headMainQ[node.level];
      node.appendToTail(head);
      sizeMainQ[node.level]++;
  
      adjust();
    }
docs: Promotes the entry to the protected region's MRU position, demoting an entry if necessary.