net.inet.tcp.tso=1 still neceesary with fxp was Re: TCP differences in 7.2 vs 7.1

Pyun YongHyeon pyunyh at
Thu May 21 03:35:36 UTC 2009

On Wed, May 20, 2009 at 05:55:29PM -0400, Michael L. Squires wrote:
> I started having speed problems after shifting from 7.1-STABLE to 
> 7.1-PRERELEASE.  They have continued with 7.2-STABLLE.
> Reverting to the 7.1-STABLE kernel eliminated the problem.
> After downloading 7.2-STABLE from at about 10:40 AM EST
> on 5/20/2009, doing a buildworld/buildkernel/installkernel/installworld
> cycle I still need to execute "net.inet.tcp.tso=1" to elminate throughput
> problems between my home system (on Comcast) and my office PC (connected
> via a Time-Warner connection).  This also affects connections to other
> systems; downloading Web pages ( speeds up after I change the TSO
> entry.
> The box in question runs NAT and has an fxp (Intel Pro100) interface 
> connected to a Comcast cable modem and an em (Intel Pro1000) interface 
> connected to the internal network.
> There are no network errors in "netstat -i" on either interface.
> The "if_fxp.c" code appears to be the May 7 version.

You should have cvs rev. of if_fxp.c.

> This is the dmesg entry for the card in question.  The system is a dual Xeon
> Supermicro 1U box, 1GB RAM, single 300GB IDE hard drive.
> fxp0: <Intel 82551 Pro/100 Ethernet> port 0xe400-0xe43f mem 
> 0xfebfd000-0xfebfdfff,0xfeb80000-0xfeb9ffff irq 27 at device 7.0 on pci0
> miibus0: <MII bus> on fxp0

Since you use both em(4) and fxp(4) I'd like to know which driver
has the issue. Instead of disabling TSO of network stack try
disabling TSO for each interface. For instance,
 1. Diable TSO of em(4) and check you see the same issue
    (ifconfig em0 -tso).
 2. Diable TSO of fxp(4) and check you see the same issue
    (ifconfig fxp0 -tso).

More information about the freebsd-stable mailing list