Arch Linux

hypothermic

Member

Registered: 2020-08-20

Posts: 6

[SOLVED] Unused network interface is extremely battery intensive

I have two network interfaces on my laptop:
- enp2s0, which I rarely use, I usually leave it down.
- wlp1s0, which I use all the time.

In PowerTop you can see the inactive interface being the most power intensive activity on my system:

Power est.    Usage           Category    Description
6.17 W        0.0 pkts/s      Device      Network interface: enp2s0 (r8169)
110 mW        52.0 pkts/s     Device      Network interface: wlp1s0 (rtl8821ce)

Why is it such power intensive if it's down all the time? It should be doing nothing. The cable is not even plugged in.

To confirm it's down:

$ ip a show enp2s0
2: enp2s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000
    link/ether ... redacted ... brd ff:ff:ff:ff:ff:ff

Last edited by hypothermic (2020-08-26 10:51:14)

Zod

Member

From: Hoosiertucky

Registered: 2019-03-10

Posts: 630

Re: [SOLVED] Unused network interface is extremely battery intensive

https://wiki.archlinux.org/index.php/Ne … interfaces

Give this a careful read.

GaKu999

Member

From: US/Eastern

Registered: 2020-06-21

Posts: 696

Re: [SOLVED] Unused network interface is extremely battery intensive

With dhcpcd enabled only for my wlp5s0 interface. 'ip a s enp9s0':

2: enp9s0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether [REDACTED] brd ff:ff:ff:ff:ff:ff

Your dhcp client is attempting to bring UP your enp2s0 interface always and leaving it UP when it fails to get a lease/connect...
You haven't said what dhcp client do you use...so if you know how, disable enp2s0 interface on it, or use a dhcp client that can be enabled for select interfaces, like dhcpcd...
Your choice really, use what fits you best.

---

My repos • Some snippets

Heisenberg might have been here.

hypothermic

Member

Registered: 2020-08-20

Posts: 6

Re: [SOLVED] Unused network interface is extremely battery intensive

https://wiki.archlinux.org/index.php/Ne … interfaces

Give this a careful read.

Thanks, this helped. I assumed "state DOWN" meant the interface was down. Confusing at first.

kagetora13

Member

Registered: 2019-10-13

Posts: 2

Re: [SOLVED] Unused network interface is extremely battery intensive

With dhcpcd enabled only for my wlp5s0 interface. 'ip a s enp9s0':

2: enp9s0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether [REDACTED] brd ff:ff:ff:ff:ff:ff

Your dhcp client is attempting to bring UP your enp2s0 interface always and leaving it UP when it fails to get a lease/connect...
You haven't said what dhcp client do you use...so if you know how, disable enp2s0 interface on it, or use a dhcp client that can be enabled for select interfaces, like dhcpcd...
Your choice really, use what fits you best.

I was reading through the notes in this post and I am not sure I understand the recommended solution. So Powertop is reporting the ethernet card is drawing power when not LAN  cable is plugged in. The suggestion is the port is being kept up by am internal DHCP server?

I am seeing something similar too on my thinkpad:

 ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp0s25: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN mode DEFAULT group default qlen 1000
    link/ether 3c:97:0e:ca:5d:91 brd ff:ff:ff:ff:ff:ff
3: wlp3s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DORMANT group default qlen 1000
    link/ether [removed]  brd ff:ff:ff:ff:ff:ff

I did use network manager and switched 'enp0s25" IPV4 and IPV6 to manual, but after a reboot it seems to use the same amount of power on discharge. I then explicitly brought down the interface :

  ip link set enp0s25 down

ip  a show enp0s25
2: enp0s25: <BROADCAST,MULTICAST> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000
    link/ether [removed] brd ff:ff:ff:ff:ff:ff

This maybe reduces power draw my 1.5 watts. So I am not sure how to implement the recommended solution here. Thanks.

Last edited by kagetora13 (2020-09-01 02:58:39)

stephematician

Member

Registered: 2023-09-01

Posts: 3

Re: [SOLVED] Unused network interface is extremely battery intensive

I've experienced the same problem, but I can't see a way to make the setting permanent; it also isn't clear if I want to? What have others done?

My system uses dhclient and networkmanager;

    ip link set enp0s2 down

reduces the power usage, but isn't the issue actually with dhclient trying to wake the device? Can this be configured to be less intensive?