code: func (rs *copResponse) MemSize() int64 {
  	if rs.respSize != 0 {
  		return rs.respSize
  	}
  
  	// ignore rs.err
  	rs.respSize += int64(cap(rs.startKey))
  	rs.respSize += int64(sizeofExecDetails)
  	if rs.CommitDetail != nil {
  		rs.respSize += int64(sizeofCommitDetails)
  	}
  	if rs.pbResp != nil {
  		// Using a approximate size since it's hard to get a accurate value.
  		rs.respSize += int64(rs.pbResp.Size())
  	}
  	return rs.respSize
  }
docs: // MemSize returns how many bytes of memory this response use