Variable Gigabit Ethernet speed?

[sheffield_nick]

(I've seen there are some older threads / bug reports about gigabit Ethernet running VERY slowly, but I think this might be a separate issue?)

I've got 5 PINE A64+ 2GB boards running Debian Jessie 8.5 base, kernel3.10.102-2-pine64-longsleep, connected to an otherwise empty 8-port gigabit switch. The speeds I'm getting with iperf are excellent , but strangely variable.

Code:

# Run server on board 1
iperf -s -V
# Run client for 100 seconds on board 2, connecting to board 1
iperf -c board1 -i 1 -t 100 -V

Between board A and B I can consistently get 828 Mbits/sec over long periods, but back the other way I only get 733 Mbits/sec. With pairs of the other boards I can consistently get 800+ Mbits/sec on some, but only 561/596/633 Mbits/sec on others.

Do you think this is simply hardware variation? 47% range!

Thanks

[fire219]

It may be hardware variation, but it'll also have to do with the real world not being a static nor ideal condition for anything electrical. Primarily, there will be differences in EMI (electrical noise) between runs, meaning that the connections run at varying speeds based on how much error correction they have to do. Also, differences in quality of Ethernet cables could be a factor, relating to the EMI issue.

That being said, if these results are more-or-less repeatable with similar results on the same pair of boards but different cables, it probably is hardware variation between boards.

[sheffield_nick]

Just an update to this issue, I seemed to narrow it down to a single board that was giving me ~480Mbps transmitting to any of the other boards, while making a faint 'chirp' noise, but could receive at ~850Mbps and make no noise.

I tried the same cable reversed, different cable and different switch port and ruled them out as causes.

I *think* it might be very slightly dodgy wiring in the Ethernet socket on that board? Plugging/unplugging a cable sometimes works consistently at full speed (in either direction) without any EMI noise, and other times is slow and makes a noise. I can't reproduce it plugging/unplugging a cable into one of my other boards.

[UnixOutlaw]

I did some tests yesterday with one of my Pine 2GB boards...  I consistently only get about 33 Mbit/s to or from Pine...  For consistency - I measured also several other devices hooked up to the same Gbit switch :

1. AMD Phenom Desktop running elementary freya, consistently get approx 933 Mbit/s (intel branded Gbit NIC)
2. i7 octacore Asus laptop running Ubuntu 15.10, consistently get ~Gbit results (USB 3.0 gbit dongle - realtek chipset)
3. HP Microserver NL40 (dual core AMD) - running FreeBSD/FreeNAS, consistently get ~Gbit results (intel chipset on/board Gbit NIC)

iperf from Pine64 to / from those three hosts?  Consistently get sub-par, lower than 100 Mbit results (e.g. ~ 33 mbit/s).  This board is plugged directly into an Edimax Gbit switch (as are the other three machines).

The pine is running the latest Debian Jessie XFCE build with the hard-coded MAC address in /boot/uEnv.txt.

Also - for comparison, I have an NTC CHIP running debian jessie kernel 4.3, with an Asus branded (AXP) USB ethernet dongle, I get ~33 Mbit/s - and this host is travelling through a TPLink router, over 500 Mbit ethernet over power to get to the switch and the iperf "server" (the AMD Phenom desktop).

[MarkHaysHarris777]

I did some tests yesterday with one of my Pine 2GB boards...  I consistently only get about 33 Mbit/s to or from Pine...  For consistency - I measured also several other devices hooked up to the same Gbit switch :

1. AMD Phenom Desktop running elementary freya, consistently get approx 933 Mbit/s (intel branded Gbit NIC)
2. i7 octacore Asus laptop running Ubuntu 15.10, consistently get ~Gbit results (USB 3.0 gbit dongle - realtek chipset)
3. HP Microserver NL40 (dual core AMD) - running FreeBSD/FreeNAS, consistently get ~Gbit results (intel chipset on/board Gbit NIC)

iperf from Pine64 to / from those three hosts?  Consistently get sub-par, lower than 100 Mbit results (e.g. ~ 33 mbit/s).  This board is plugged directly into an Edimax Gbit switch (as are the other three machines).

The pine is running the latest Debian Jessie XFCE build with the hard-coded MAC address in /boot/uEnv.txt.

Also - for comparison, I have an NTC CHIP running debian jessie kernel 4.3, with an Asus branded (AXP) USB ethernet dongle, I get ~33 Mbit/s - and this host is travelling through a TPLink router, over 500 Mbit ethernet over power to get to the switch and the iperf "server" (the AMD Phenom desktop).

would you please post your results using iperf3.

Also... please take the poll on the ethernet sub-forum, and provide your data as per the instructions on the first post. Thanks, much appreciated !