[arch-general] Performance with Linux Bridge

[Carlos Ferreira]

Hello to all

I'm using Arch Linux in a SuperMicro A1SAi-2750F motherboard and I'm having
performance issues while bridging 3 Ethernet Gigabit network interfaces.
The 4th network interface of that motherboard, is used to connect to the
ISP.
This setup is my Router/server and I use the 3 bridged interfaces to
connect my home network.

But now, I'm noticing severe performance issues.


I conducted a small iperf3 test. The scenario was:
PC A (100Mbps) <---> Server Ether 1(1Gbps) <---> Linux Bridge (br0) <--->
Server Ether 2 (1Gbps) <---> PC B (1Gbps)

The result:
Connecting to host 192.168.123.136, port 5201
[  4] local 192.168.123.4 port 55462 connected to 192.168.123.136 port 5201
[ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
[  4]   0.00-1.00   sec  1.47 MBytes  12.3 Mbits/sec   56   9.90
KBytes
[  4]   1.00-2.00   sec  1.16 MBytes  9.70 Mbits/sec   50   8.48
KBytes
[  4]   2.00-3.00   sec  1.10 MBytes  9.25 Mbits/sec   30   12.7
KBytes
[  4]   3.00-4.00   sec  1.14 MBytes  9.52 Mbits/sec   40   5.66
KBytes
[  4]   4.00-5.00   sec  1.04 MBytes  8.76 Mbits/sec   37   8.48
KBytes
[  4]   5.00-6.00   sec  1.19 MBytes  9.96 Mbits/sec   40   12.7
KBytes
[  4]   6.00-7.00   sec  1.14 MBytes  9.55 Mbits/sec   46   7.07
KBytes
[  4]   7.00-8.00   sec  1.02 MBytes  8.55 Mbits/sec   39   14.1
KBytes
[  4]   8.00-9.00   sec  1.14 MBytes  9.52 Mbits/sec   47   12.7
KBytes
[  4]   9.00-10.00  sec  1.04 MBytes  8.72 Mbits/sec   35   11.3
KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.00  sec  11.4 MBytes  9.58 Mbits/sec  420             sender
[  4]   0.00-10.00  sec  11.4 MBytes  9.57 Mbits/sec
receiver


Then i conducted another iperf3 test with a different scenario:
PC A (100Mbps) <---> Server Ether 1 (1Gbps) <---> Linux Bridge (br0)

The result:
Connecting to host 192.168.123.1, port 5201
[  4] local 192.168.123.4 port 58982 connected to 192.168.123.1 port 5201
[ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
[  4]   0.00-1.00   sec  11.3 MBytes  94.5 Mbits/sec    0   24.0
KBytes
[  4]   1.00-2.00   sec  11.2 MBytes  94.1 Mbits/sec    0   24.0
KBytes
[  4]   2.00-3.00   sec  11.2 MBytes  94.1 Mbits/sec    0   24.0
KBytes
[  4]   3.00-4.00   sec  11.2 MBytes  94.1 Mbits/sec    0   24.0
KBytes
[  4]   4.00-5.00   sec  11.2 MBytes  94.2 Mbits/sec    0   24.0
KBytes
[  4]   5.00-6.00   sec  11.2 MBytes  94.3 Mbits/sec    0   24.0
KBytes
[  4]   6.00-7.00   sec  11.2 MBytes  94.1 Mbits/sec    0   24.0
KBytes
[  4]   7.00-8.00   sec  11.2 MBytes  94.1 Mbits/sec    0   24.0
KBytes
[  4]   8.00-9.00   sec  11.2 MBytes  94.1 Mbits/sec    0   24.0
KBytes
[  4]   9.00-10.00  sec  11.2 MBytes  94.2 Mbits/sec    0   24.0
KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.00  sec   112 MBytes  94.2 Mbits/sec    0             sender
[  4]   0.00-10.00  sec   112 MBytes  94.1 Mbits/sec
receiver

iperf Done.


Does anyone know if this low performance behaviour by a Linux bridge is
"normal" or, if it is a configuration problem?
I disabled iptables. Despite gaining a little improvement, I still have
severe performance issues.

Can anyone provide some light in this case?
Thank you!

Carlos Miguel Ferreira