private static LlapCacheableBuffer removeFromLocalList(
      LlapCacheableBuffer tail, LlapCacheableBuffer current) {
    if (current == tail) {
      tail = current.prev;
    } else {
      current.next.prev = current.prev;
    }
    if (current.prev != null) {
      current.prev.next = current.next;
    }
    current.prev = null;
    current.next = null;
    return tail;
  }
Flushes all BPWrappers which will in turn clear IO-Threads' threadlocal buffers.
llap-server/src/java/org/apache/hadoop/hive/llap/cache/LowLevelLrfuCachePolicy.java