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#1 2018-11-29 17:26:22

emacsomancer
Member
Registered: 2014-09-20
Posts: 198

Slow internet via ethernet on one machine, but only under Arch?

My main desktop machine, which has been running Arch for 5+ years, is suddenly getting very slow download speeds over ethernet.

I've tried plugging other machines into the same ethernet cable, and they get the normal, expected speeds.

When I boot the desktop into another distro via usbstick, I can get normal download speeds over ethernet.

So only this particular machine is affected, and only when I'm booted into Arch (though I've run Arch on this machine for years without ethernet issues).

What should I try for diagnosing the issue?

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#2 2018-11-29 17:30:36

schard
Member
From: Hannover
Registered: 2016-05-06
Posts: 124

Re: Slow internet via ethernet on one machine, but only under Arch?

What do you consider normal?
What kind of measurements did you perform?
What are the concrete values of transmission speed and packet loss?
A useful diagnostic tool might be iperf3.

Last edited by schard (2018-11-29 17:32:35)

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#3 2018-11-29 17:44:01

emacsomancer
Member
Registered: 2014-09-20
Posts: 198

Re: Slow internet via ethernet on one machine, but only under Arch?

schard wrote:

What do you consider normal?
What kind of measurements did you perform?
What are the concrete values of transmission speed and packet loss?
A useful diagnostic tool might be iperf3.

Speedtest via testmy.net

Under Arch I'm currently getting like 15mbps, while if I reboot into another distro I get around 250mbps. (The latter is the normal sort of speeds I used to get on this machine under Arch.)

Edit:

with iperf3, using another ethernet connected machine, I only get about 65Mbps transfer to the machine in question, whereas to another machine connected via WiFi I can get about 188Mbps via iperf3.

and when I boot the problematic machine into the Pop!_OS install usb, I can get around 950Mbps between it and another ethernet-connected machine via iperf3.

Last edited by emacsomancer (2018-11-29 18:23:21)

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#4 2018-11-30 08:54:27

schard
Member
From: Hannover
Registered: 2016-05-06
Posts: 124

Re: Slow internet via ethernet on one machine, but only under Arch?

So the 950 Mbps suggests, that your machine has a gigabit ethernet port.
So you should concentrate your network throughput tests to those with a counterpart that also hast at least a gigabit ethernet connection to rule out other possible bottlenecks or technical issues e.g. with WiFi.
Please also post the actual commands and their respective outputs that you run.

Last edited by schard (2018-11-30 08:55:43)

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#5 2018-11-30 15:32:45

seth
Member
Registered: 2012-09-03
Posts: 8,981

Re: Slow internet via ethernet on one machine, but only under Arch?

ip l

If you know the interface (listed with above command, it's not "lo"):

ethtool <interface>

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#6 2018-11-30 19:19:54

loqs
Member
Registered: 2014-03-06
Posts: 6,419

Re: Slow internet via ethernet on one machine, but only under Arch?

How recently did this start happening (can you give an estimate on the time frame roughly hours, days weeks)

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#7 2018-12-01 18:17:26

paulkerry
Member
From: Sheffield, UK
Registered: 2014-10-02
Posts: 374

Re: Slow internet via ethernet on one machine, but only under Arch?

Perhaps a kernel driver update has caused this - which kernel version are you using...

uname -a

and which kernel module is in use for your ethernet...

lspci -v

Have you tried the lts kernel?

Last edited by paulkerry (2018-12-01 18:22:53)

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