public void pageWritten(final int bytesWritten,
                          final long writeStartedAtNs) {
    assert bytesWritten >= 0 : "bytesWritten must be >=0, " + bytesWritten;
    totalPagesWritten.incrementAndGet();
    totalBytesWritten.addAndGet(bytesWritten);
    if (MEASURE_TIMESTAMPS) {
      totalPagesWriteNs.addAndGet(System.nanoTime() - writeStartedAtNs);
    }
  }
public void pageWritten(final int bytesWritten,
                          final long writeStartedAtNs)