network perf : em driver ?

Dominic Marks dom at
Fri Jan 12 01:52:40 PST 2007

On Fri, 12 Jan 2007 10:00:47 +0100
Patrick Proniewski <patpro at> wrote:

> Hello,
> I'm the happy owner of a Tyan Tiger i7520SD motherboard, sporting two  
> ethernet ports using a Intel 82571EB GbE controller and running  
> FreeBSD 6.2 RC1. FreeBSD uses the em driver for this ports:
> dmesg excerpt:
> em0: <Intel(R) PRO/1000 Network Connection Version - 6.2.9> port  
> 0x2000-0x201f mem 0xd8020000-0xd803ffff,0xd8000000-0xd801ffff irq 16  
> at device 0.0 on pci3
> ifconfig output:
>          options=b<RXCSUM,TXCSUM,VLAN_MTU>
>          inet netmask 0xffffff00 broadcast
>          ether 00:e0:81:42:e3:aa
>          media: Ethernet autoselect (1000baseTX <full-duplex>)
>          status: active
> The box uses its 100baseT fxp driven eth port for internet access,  
> and shares this access with a Mac OS X plugged on the em0 interface.  
> I've set up pf with firewall and nat rules to act as a gateway. Both  
> machines are in "Ethernet autoselect (1000baseTX <full-duplex>)" and  
> linked with a direct ethernet wire.
> File transfert through em0 looks quite slow : at best 17 MB/s (scp  
> gives better results than http, tested with a 120MB file)
> File copy, from one HDD to another or from one HDD to /dev/null,  
> ranges from 30 to 48 MB/s on the FreeBSD side (SATA HD).

Try testing FTP. SCP will be doing encryption which will slow
the process down. I can't say which HTTP would be slower than

I have some Dell's with similar specification which will
happily FTP back and forth at around 40MB/s which is reasonable.

> I would like to know if there is a good method to find the bottleneck  
> and to get rid of it. How comes my GbE is so slow ?

This is a dedicated network right? No other traffic?


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