@Override
    public boolean start() throws IOException {
      boolean isFirst = RUNNER_COUNT.getAndIncrement() == 0;
      if (isFirst) {
        try {
          START_COMPACTOR_LATCH.await();
          return super.start();
        } catch (InterruptedException ex) {
          throw new RuntimeException(ex);
        }
      }
      return super.start();
    }
This test is for HBASE-26494, test the {@link RefCnt} behaviors in {@link ImmutableMemStoreLAB}
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestHStore.java