Network speed limitation(100M) of Route-based ipsec tunnel

[kui.jin]

I am trying to test the network speed with Route-based ipsec tunnel, and my environment is built in the same esxi server:
test-client-------opnsense1------------------------------opnsense2--------test-server

There is a routed-based ipsec tunnel(VTI mode) at WAN(1000M) of opnsense1 and opnsense2, and each of them has a test linux connecting at LAN.
The test tool is iperf3, and the traffic is running into the ipsec tunnel correctly.  But i find that the network speed is limited at 100M, the max speed is about 90M+(see the attachment).

Is there a limitation for the virtual interface of Route-based ipsec tunnel as  100M? And how can i increase the speed to be over 500M?