OVS-dpdk bond with ConnectX-5

Hello there,
I used OVS-dpdk bond with ConnectX-5 . The configuration is following:
ovs-vsctl add-br br-int – set bridge br-int datapath_type=netdev
ip addr add ip/mask dev br-int
ovs-vsctl add-bond br-int dpdkbond dpdk0 dpdk1 – set Interface dpdk0 type=dpdk options:dpdk-devargs=0000:98:00.0 – set Interface dpdk1 type=dpdk options:dpdk-devargs=0000:98:00.1

test throughput with iperf3, the result is 718 Mbits/sec.

bond information is following:
root@POD65-CLU01-GPU02:~# ovs-appctl bond/show dpdkbond
---- dpdkbond ----
bond_mode: balance-slb
bond may use recirculation: no, Recirc-ID : -1
bond-hash-basis: 0
updelay: 0 ms
downdelay: 0 ms
next rebalance: 4444 ms
lacp_status: off
lacp_fallback_ab: false
active slave mac: b8:ce:f6:91:99:95(dpdk0)

slave dpdk0: enabled
active slave
may_enable: true
hash 15: 222 kB load

slave dpdk1: enabled
may_enable: true

I tried active−backup mode, the result is same.

But I just deleted one of dpdk port with command:
ovs-vsctl del-bond-iface dpdkbond dpdk1

the result of throughput is 5.31 Gbits/sec.

Looks like ovs-dpdk bond would seriously influence throughput of network.

dpdk version: 19.11.10
ovs version: 2.13.3

Is there any configuration missing?
Any help would be appreciated.
Thank you very much!
Longzhen