public void makeFlushMemTableCP(long memTableId) {
    infoLock.lock();
    long start = System.nanoTime();
    try {
      MemTableInfo memTableInfo = memTableId2Info.get(memTableId);
      if (memTableInfo == null) {
        return;
      }
      memTableInfo.setFlushed();
      if (!memTableInfo.isPinned()) {
        memTableId2Info.remove(memTableId);
      }
      Checkpoint checkpoint =
          new Checkpoint(
              CheckpointType.FLUSH_MEMORY_TABLE, Collections.singletonList(memTableInfo));
      logByCachedByteBuffer(checkpoint);
    } finally {
      WRITING_METRICS.recordMakeCheckpointCost(
          CheckpointType.FLUSH_MEMORY_TABLE, System.nanoTime() - start);
      infoLock.unlock();
    }
  }
Make checkpoint for flush memTable info.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/wal/checkpoint/CheckpointManager.java