High CPU usage on Hyper-v Windows server 2019 when download speed at 200mb

[leeyuky]

Name     OPNsense.localdomain
Versions     OPNsense 20.1-amd64
FreeBSD     11.2-RELEASE-p16-HBSD
OpenSSL     1.1.1d 10 Sep 2019

Updates      Click to check for updates.

CPU Type      Intel(R) Core(TM) i5-4590T CPU @ 2.00GHz (4 cores)

NIC             two hyper-v virtual nics as wan and lan

physical nic: broadcom

Hi,opnsense works perfectly most the time, but while pulling download speed at 200mb cpu usage can be 58% arising from nearly zero for 4590t,which is werid.

i tried a clean installation of opnsense and it is the same.then i tried pfsense at the same speed cpu usage is 22%.

i thought maybe its the virtual nic drive so i tried to pass through broadcom nic but opnsense does't support this nic,and lan can't be passthroughed cuz i need a openwrt firmware to deal with the grat firewall of china which uses lan virtual swith.

All ideas are welcome!