timeout param not work, request retrans from 2ms

[MCxiaofang]

I have two ConnectX-5 network cards for RDMA transmission experiments.
I introduced a 40ms delay on the link using the damage meter, so I may need to increase the timeout time per request (the default 64ms (timeout=14) may be sufficient).
However, when I used wireshark to capture packets, I found that the network adapter retransmitted each request 5 times, at intervals of 2ms,4ms,8ms,16ms
Even if I increase the -u parameter, it doesn't work

ib_read_bw -F -d mlx5_1 -s 262144 -n 1000 -t 1024 -l 200 -u 18