[Bug 894608] [NEW] Implementing a bridge slows 10G network

[Mike Imelfort]

Public bug reported:

Installing bridge-utils and then setting up a bridge in
/etc/netwrok/interfaces decimates my netwrok speed. Uninstalling the
package and doing a reboot restores the speed.

This bug was originally posted here:
https://bugs.launchpad.net/qemu/+bug/861141 but I now realise it is
bridge-utils specific.

Hardware:
I have two identical machines (DELL poweredge R815), each with Broadcom NetXtreme II BCM57711 10-Gigabit PCIe connected via a 10G switch.
Each machine runs 4 socket 12 core AMD Opteron(tm) Processor 6174 and 128GB of ram

Software:
Both machines ar running ubuntu server 10.04 lts Kernels are:
Linux whitlam 2.6.32-28-server #55-Ubuntu SMP Mon Jan 10 23:57:16 UTC 2011 x86_64 GNU/Linux
Linux fraser 2.6.32-28-server #55-Ubuntu SMP Mon Jan 10 23:57:16 UTC 2011 x86_64 GNU/Linux

I have installed iperf on both machines.

The tests here involve running whitlam as the iperf server and fraser as the client.
On whitlam I run:
bioadmin at whitlam:~# iperf -sm

On fraser I run:
bioadmin at fraser:~# iperf -c whitlam -d

before installation I get:
bioadmin at whitlam:~# iperf -sm
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
[ 5] local 10.168.48.14 port 5001 connected with 10.168.48.13 port 37960
------------------------------------------------------------
Client connecting to 10.168.48.13, TCP port 5001
TCP window size: 110 KByte (default)
------------------------------------------------------------
[ 6] local 10.168.48.14 port 49627 connected with 10.168.48.13 port 5001
Waiting for server threads to complete. Interrupt again to force quit.
[ 5] 0.0-10.0 sec 10.8 GBytes 9.23 Gbits/sec
[ 5] MSS size 1448 bytes (MTU 1500 bytes, ethernet)
[ 6] 0.0-10.0 sec 10.6 GBytes 9.11 Gbits/sec
[ 6] MSS size 1448 bytes (MTU 1500 bytes, ethernet)

Which is nice.

Next I run:

sudo aptitude -y install bridge-utils

and then I add a bridge to the interfaces file like thus:

FROM:
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth4
iface eth4 inet static
	address xx.xx.xx.xx
	netmask 255.255.255.0
	network xx.xx.xx.0
	broadcast xx.xx.xx.255
	gateway xx.xx.xx.1
	# dns-* options are implemented by the resolvconf package, if installed
	dns-nameservers blah blah

TO:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
#auto eth4
#iface eth4 inet manual

auto br0
iface br0 inet static
	address xx.xx.xx.13
	netmask 255.255.255.0
	network xx.xx.xx.0
	broadcast xx.xx.xx.255
	gateway xx.xx.xx.1
	bridge_ports eth4
	bridge_stp off
	# dns-* options are implemented by the resolvconf package, if installed
	dns-nameservers blah blah

And restart networking

sudo /etc/init.d/netwroking restart

Which results in:
bioadmin at whitlam:~# iperf -sm
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
[ 4] local 10.168.48.14 port 5001 connected with 10.168.48.13 port 56405
------------------------------------------------------------
Client connecting to 10.168.48.13, TCP port 5001
TCP window size: 1.25 MByte (default)
------------------------------------------------------------
[ 6] local 10.168.48.14 port 57001 connected with 10.168.48.13 port 5001
Waiting for server threads to complete. Interrupt again to force quit.
[ ID] Interval Transfer Bandwidth
[ 4] 0.0-10.0 sec 10.5 GBytes 9.00 Gbits/sec
[ 4] MSS size 1448 bytes (MTU 1500 bytes, ethernet)
[ 6] 0.0-10.0 sec 2.51 GBytes 2.15 Gbits/sec
[ 6] MSS size 1448 bytes (MTU 1500 bytes, ethernet)

Note that the connection from the machine with bridge-utils installed
(fraser) to the other machine (whitlam) is not affected. Only the
connection from whitlam to fraser.

Both machines are fresh installs with nfs-common, iperf installed.
Fraser also has bridge-utils

Any help is very much appreciated!

** Affects: bridge-utils (Ubuntu)
     Importance: Undecided
         Status: New

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Title:
  Implementing a bridge slows 10G network

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