protected synchronized EvictionNode unlinkHeadEntry() {
    EvictionNode evictionNode = head.next();
    if (evictionNode == tail) {
      return null; // end of list
    }

    unlinkEntry(evictionNode);
    return evictionNode;
  }
Remove and return the head entry in the list
geode-core/src/main/java/org/apache/geode/internal/cache/eviction/AbstractEvictionList.java