Why blktrace didn't trace requests merge?

[Jianpeng Ma]

Hi all:
        I used blktrace to trace some io.But i can't find requests merge. I 
searched the code and did't not find.
        Why? 
                                                                        
Thanks!
JianpengN�Р骒r��y����b�X�肚�v�^�)藓{.n�+�伐�{��赙zXФ�≤�}��财�z�&j:+v�����赙zZ+��+zf＂�h���~����i���z��wア�?�ㄨ��&�)撷f��^j谦y�m��@A�a囤�
0鹅h���i