em interface slow down on 8.0R

[Elliot Finley]

On Mon, Nov 30, 2009 at 6:29 PM, Hiroki Sato <hrs at freebsd.org> wrote:

> Jack Vogel <jfvogel at gmail.com> wrote
>  in <2a41acea0911301119j1449be58y183f2fe1d1112a68 at mail.gmail.com>:
>
> jf> I will look into this Hiroki, as time goes the older hardware does not
> jf> always
> jf> get test cycles like one might wish.
>
>
Here's some more info to throw into the mix.  I have several new boxes
running 8-Stable (a few hours after release).

Leaving all sysctl at default, I get around 400mbps testing with netperf or
iperf.  If I set the following on the box running 'netserver' or 'iperf -s':

kern.ipc.maxsockbuf=16777216
net.inet.tcp.recvspace=1048576

then I can get around 926mbps.  But then if I make those same changes on the
box running the client side of netperf or iperf the performance drops back
down to around 400mbps.

All boxes have the same hardware.  they have two 4-port Intel NICS in them.

em1 at pci0:5:0:1: class=0x020000 card=0x10a48086 chip=0x10a48086 rev=0x06
hdr=0x00
    vendor     = 'Intel Corporation'
    device     = '82571EB Gigabit Ethernet Controller'
    class      = network
    subclass   = ethernet

any pointers on further network tuning to get bidirectional link saturation
would be much appreciated.  These boxes are not in production yet, so anyone
that would like to have access to troubleshoot, just ask.

TIA
Elliot