APP may influence ovs offload

Hi all,
With running DNS_Filter app on the host1, I use iperf to test the bindwith. Host1 to Host2 is 23.5Gbits/s. But Host2 to Host1 is about 5-7Gbits/s. I don’t know why this phenomenon occurs. I guess that ovs offload is wrong. But I can not solve it.
Besides that, I use ib_send_bw to test rdma. It does not work. Is rdma not working when app (e.g. dns_filer, url_filter etc.) is running?