Ubuntu ethernet bridge limited to 1Gbs?

I have an Intel 522SFP network adapter in a Ubuntu Server machine and I am facing a strange issue with speed.

If I use it "directly" with this netplan (enp1s0f0 interface) :

# This is the network config written by 'subiquity'
network:
  ethernetsenp1s0f0:
    enp5s0:
      dhcp4: false
      dhcp6: false
    enp1s0f0:
      addresses:
      - 192.168.11.203/24
    enp1s0f1:
      addresses:
      - 192.168.10.203/24
  bridges:
    br0:
      interfaces: [enp5s0]
      addresses:
      - 192.168.1.203/24
      nameservers:
        addresses:
        - 192.168.1.1
        search: []
      routes:
      - to: default
        via: 192.168.1.1
  version: 2

I get a iperf3 throughput speed of about 8Gbps UP or 5Gbps DOWN on 192.168.11.203. This is not 10Gbps but yet acceptable for my use. I should investigate on it later to understand why I don't get my full 10Gbps speed.

But, the strange part is when I setup a bridge (this server is a KVM host) on the enp1s0f0 like so :

# This is the network config written by 'subiquity'
network:
  ethernets
    enp5s0:
      dhcp4: false
      dhcp6: false
    enp1s0f0:
      dhcp4: false
      dhcp6: false
    enp1s0f1:
      addresses:
      - 192.168.10.203/24
  bridges:
    br0:
      interfaces: [enp5s0]
      addresses:
      - 192.168.1.203/24
      nameservers:
        addresses:
        - 192.168.1.1
        search: []
      routes:
      - to: default
        via: 192.168.1.1
    brsf0:
      interfaces: [enp1s0f0]
      addresses:
      - 192.168.11.203/24
  version: 2

Then my iperf3 throughput drop down to 1Gbps UP/DOWN.. It's like a brigde is limited to 1Gbps. Am I missing anything in my netplan setup ?

Thank for your help.

After disabling the bridge filtering, I was able to higher speed. But still not able the throughput which was limited by the CPU + NIC(offloading the traffic to CPU instead of it handling)

update the following files to 0 under proc/sys/net/bridge/:

• bridge-nf-call-arptables
• bridge-nf-call-iptables
• bridge-nf-call-ip6tables

Source: http://ebtables.netfilter.org/documentation/bridge-nf.html