you forgot to enable sysctl net.inet.ip.forwarding=1 on the first test.  
Turn that on, then re-measure the speeds of the bridge.

On 2007 May 15 (Tue) at 19:04:47 +0200 (+0200), Renaud Allard wrote:
:Hello,
:
:I just had the opportunity to test some Fluke network equipment, notably
:one which is able to throughput test gigabit networks.
:
:I installed a Nexcom NSA1086 with OpenBSD 4.1-stable and did some tests.
:The NSA1086 units are equipped with a Pentium IV 3.2Ghz (hyperthreading
:disabled), and 1Gb ram. They have 4 sk gigabit interfaces, and 4 msk
:gigabit interfaces. Here are the tests:
:
:**********
:ifconfig sk0 up
:ifconfig sk1 up
:ifconfig bridge0 create
:ifconfig bridge0 up
:brconfig bridge0 add sk0
:brconfig bridge0 add sk1
:sysctl kern.maxclusters=256000
:
:Then I connected the fluke analyzers to both sk ports. connections were
:correctly seen at 1000 base T full Duplex. then I started a throughput
:test on 1Gbps, and I was extremely surprised to see how performance was
:very poor. The throughput was only about 77Mbps.
:
:***************
:
:Seeing that I decided to try on msk interfaces and got about the same
:"performance".
:
:***************
:
:Then I configured routing between two interfaces.
:ifconfig sk2 inet 192.168.0.1 255.255.255.0
:ifconfig sk3 inet 192.168.1.1 255.255.255.0
:sysctl net.inet.ip.forwarding=1
:sysctl kern.maxclusters=256000
:
:I did the throughput test, and got about 500Mbps both on sk and msk,
:with the CPU keeping quiet.
:
:**************
:
:So the weak performance doesn't seem related to the bus, the CPU, or the
:sk/msk drivers. Has someone an explanation on why I get this kind of
:behavior?
:


--
Anthony's Law of Force:
	Don't force it; get a larger hammer.