/**
   * @param entry Entry to touch.
   * @return {@code True} if queue has been changed by this call.
   */
  private boolean touch(GridCacheEntry<K, V> entry) {
    Node<GridCacheEntry<K, V>> node = entry.meta(meta);

    // Entry has not been enqueued yet.
    if (node == null) {
      while (true) {
        node = queue.offerLastx(entry);

        if (entry.putMetaIfAbsent(meta, node) != null) {
          // Was concurrently added, need to clear it from queue.
          queue.unlinkx(node);

          // Queue has not been changed.
          return false;
        } else if (node.item() != null) {
          if (!entry.isCached()) {
            // Was concurrently evicted, need to clear it from queue.
            queue.unlinkx(node);

            return false;
          }

          return true;
        }
        // If node was unlinked by concurrent shrink() call, we must repeat the whole cycle.
        else if (!entry.removeMeta(meta, node)) return false;
      }
    }

    // Entry is already in queue.
    return false;
  }
  /** {@inheritDoc} */
  @Override
  public void onEntryAccessed(boolean rmv, GridCacheEntry<K, V> entry) {
    if (!rmv) {
      if (!entry.isCached()) return;

      // Shrink only if queue was changed.
      if (touch(entry)) shrink();
    } else {
      Node<GridCacheEntry<K, V>> node = entry.removeMeta(meta);

      if (node != null) queue.unlinkx(node);
    }
  }
  /** Shrinks FIFO queue to maximum allowed size. */
  private void shrink() {
    int max = this.max;

    int startSize = queue.sizex();

    for (int i = 0; i < startSize && queue.sizex() > max; i++) {
      GridCacheEntry<K, V> entry = queue.poll();

      if (entry == null) break;

      if (!entry.evict()) {
        entry.removeMeta(meta);

        touch(entry);
      }
    }
  }