Gigabit Ethernet performance with Realtek 8111E

[Rick Macklem]

bevan wrote:
> Hi!
> 
> I've got a small NAS with Intel D525MW (Atom) board inside using
> FreeBSD
> 9.0-RC1 as operating system. It has an onboard Realtek 8111E ethernet
> adapter. I'm experiencing heavy performance problems when transfering
> files from a specific PC in my network to that NAS. I did the
> following
> tests by transfering large amount of data between the diferrent
> machines
> (using dd and nc):
> 
> NAS -> Linux1: ~ 400Mbit/s
> NAS -> Linux2: ~ 400Mbit/s
> Linux1 -> NAS: heavy fluctuation, between 700Mbit/s and 0bit/s
> Linux2 -> NAS: ~ 400Mbit/s
> Linux1 -> Linux2: ~ 400Mbit/s
> Linux2 -> Linux1: ~ 400Mbit/s
> 
> As you can see everythink works fine except for transfering data from
> Linux1 to that NAS box. The following graph shows the problem:
> http://dl.dropbox.com/u/25455527/network-problems.png
> 
> While the transfer rate drops to zero the NAS also has a very bad ping
> up to one second. Ping of Linux1 is perfectly fine during these
> outages.
> 
> I also had a quick look on the data stream with wireshark on Linux1
> and
> it shows a lot of TCP Dup ACK (up to 263 Dup ACKs created by NAS for
> one
> frame).
> 
> What can be eliminated as a cause is:
> - Switch (I tried connecting Linux1 and NAS directly)
> - Cable (I changed that a few times)
> - Harddisk I/O (I'm only writing from /dev/zero to /dev/null)
> 
> The sevirity of that problem varies from one minute to another but can
> always be reproduced with a few tries.
> 
> When limiting either NAS or Linux1 to 100Mbit I'm getting a steady
> transfer rate of about 90Mbit/s.
> When decreasing the MTU on NAS to 1200 the problem seems to disappear,
> getting a transfer rate of about 160Mbit/s.
> 
> ifconfig re0:
> > re0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu
> > 1500
> > 	options=388b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWCSUM,WOL_UCAST,WOL_MCAST,WOL_MAGIC>
> > 	ether 38:60:77:3e:af:a5
> > 	inet 192.168.178.54 netmask 0xffffff00 broadcast 192.168.178.255
> > 	nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
> > 	media: Ethernet autoselect (1000baseT <full-duplex>)
> > 	status: active
> 
try typing:
# sysctl dev.re.0.stats=1
- this will dump out the stats on the chip
  if the "Rx missed frames" count is non-zero, you're probably snookered,
  to put it technically:-)
  - That's what I get for a re chip is this laptop and I haven't found
    a way around it. I just live with flakey net performance.

rick

> pciconf -lv:
> > re0 at pci0:1:0:0: class=0x020000 card=0xd6258086 chip=0x816810ec
> > rev=0x06 hdr=0x00
> >     vendor = 'Realtek Semiconductor Co., Ltd.'
> >     device = 'RTL8111/8168B PCI Express Gigabit Ethernet controller'
> >     class = network
> >     subclass = ethernet
> 
> Because Linux1 seems to be involved in that problem: It's running
> Linux
> 3.0 and it has an "Atheros Communications AR8121/AR8113/AR8114"
> onboard.
> 
> Does anyone have an idea what could be the problem here? Decreasing
> the
> MTU is some kind of solution but the performance is still not optimal
> and a MTU of 1500 should be no problem.
> 
> Greetings,
> Michael Laß
> 
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