low network speed

[Rick Macklem]

Eugene M. Zheganin wrote:
> Hi.
> 
> I'm suffering from low network performance on one of my FreeBSDs.
> I have an i386 8.2-RELEASE machine with an fxp(4) adapter. It's
> connected though a bunch of catalysts 2950 to another 8.2. While other
> machines in this server room using the same sequence of switches and
> the
> same target source server (which, btw, is equipped with an em(4) and a
> gigabit link bia catalyst 3750) show sufficient speed, this particular
> machine while using scp starts with a speed of 200 Kbytes/sec and
> while
> copying the file shows speed about 600-800 Kbytes/sec.
> 
> I've added this tweak to the sysctl:
> 
> net.local.stream.recvspace=196605
> net.local.stream.sendspace=196605
> net.inet.tcp.sendspace=196605
> net.inet.tcp.recvspace=196605
> net.inet.udp.recvspace=196605
> kern.ipc.maxsockbuf=2621440
> kern.ipc.somaxconn=4096
> net.inet.tcp.sendbuf_max=524288
> net.inet.tcp.recvbuf_max=524288
> 
> With these settings the copying starts at 9.5 Mbytes/sec speed, but
> then, as file is copying, drops down to 3.5 Megs/sec in about
> two-three
> minutes.
> 
> Is there some way to maintain 9.5 Mbytes/sec (I like this speed more)
> ?
> 
You might want to try disabling the hardware checksumming via ifconfig.
(I very vaguely recall doing that for a fxp(4) interface some time ago,
 but am probably completely wrong.:-)

rick

> 
> Thanks.
> Eugene.
> 
> P.S. This machine also runs zfs, I don't know if it's important but I
> decided to mention it.
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