Low throughout on PPPoE

Hi ,
I have Vyos configured as PPPoE server. My Current Hardware Configurations are as below.

Model name: Intel® Xeon® CPU E5620 @ 2.40GHz
Ethernet controller: Intel Corporation 82599ES 10-Gigabit SFI/SFP+ Network Connection (rev 01)
Total online memory: 32G

As soon as i hit traffic around 1.2Gbps browsing experience is very slow End user.

Please help in configuring best utilisation for my hardware and number of PPPoE client this server can handle.

I also have NAT enabled on this server and most of the users will be on NAT on this Server