Awful forwarding rate [7.2-Release, igb]

[Oleg Baranov]

Hello!

I have extremely low forwarding speed on 7.2-Release box with dual Intel 
82575.

Box "B" with dual 82575 nic is connected between A and C using gigabit 
swithes
A <---> B <----> C


iperf run from A to C shows:

$ iperf -w 128k -c 192.168.111.3    
------------------------------------------------------------
Client connecting to 192.168.111.3, TCP port 5001
TCP window size:   129 KByte (WARNING: requested   128 KByte)
------------------------------------------------------------
[  3] local 192.168.1.15 port 51077 connected with 192.168.111.3 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-11.2 sec    160 KBytes    117 Kbits/sec



the same run from A to B shows:

]$ iperf -w 128k -c 192.168.1.153
------------------------------------------------------------
Client connecting to 192.168.1.153, TCP port 5001
TCP window size:   129 KByte (WARNING: requested   128 KByte)
------------------------------------------------------------
[  3] local 192.168.1.15 port 60907 connected with 192.168.1.153 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  1.09 GBytes    933 Mbits/sec


and from B to C shows:

$ iperf -w 128k -c 192.168.111.3
------------------------------------------------------------
Client connecting to 192.168.111.3, TCP port 5001
TCP window size:   129 KByte (WARNING: requested   128 KByte)
------------------------------------------------------------
[  3] local 192.168.111.254 port 64290 connected with 192.168.111.3 port 
5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  1.08 GBytes    930 Mbits/sec


Boxes B and C are both dual quad-core e5420 CPUs on Supermicro X7DWN+ 
motherboard.
As A I tried several machines including dual quad-core Phenom system as 
well as some portable PCs and workstations residing in the same LAN.

Here is ifconfig from B

$ ifconfig
igb0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
    options=19b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4>
    ether 00:30:48:c8:19:66
    inet 192.168.1.153 netmask 0xffffff00 broadcast 192.168.1.255
    media: Ethernet autoselect (1000baseTX <full-duplex>)
    status: active
igb1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
    options=19b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4>
    ether 00:30:48:c8:19:67
    media: Ethernet autoselect (1000baseTX <full-duplex>)
    status: active
    lagg: laggdev lagg0
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> metric 0 mtu 16384
    inet6 fe80::1%lo0 prefixlen 64 scopeid 0x3
    inet6 ::1 prefixlen 128
    inet 127.0.0.1 netmask 0xff000000
lagg0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
    options=19b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4>
    ether 00:30:48:c8:19:67
    inet 192.168.111.254 netmask 0xffffff00 broadcast 192.168.111.255
    media: Ethernet autoselect
    status: active
    laggproto lacp
    laggport: igb1 flags=1c<ACTIVE,COLLECTING,DISTRIBUTING>
gif0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> metric 0 mtu 1280
    tunnel inet 192.168.1.153 --> 192.168.1.156
    inet 192.168.111.254 --> 192.168.112.254 netmask 0xffffffff


I tried to remove lagg & gif interfaces, boot GENERIC kernel and even 
set up same net config from LiveFS cd - nothing helps. Forwarding speed 
sometimes goes up to 1-2 Mbit/sec while local speeds are always above 
900Mbit.
System load is less 1%, logs contain nothing interesting...

Any clues and ideas would be appreciated!!!!