• PCI power control "auto" for unused ethernet device kills server

    mgutt

    By mgutt

      • Minor

    I want to save some energy, so I set the power control of all my PCI devices "auto". But if I do this with my unused ethernet device, this will crash the server if I change afterwards some network settings through the WebGUI (or execute ethtool as in the following example):

     

    In Unraid: 

    # lspci -nn
...
07:00.0 Ethernet controller [0200]: Intel Corporation Ethernet Controller I225-LM [8086:15f2] (rev 03)

# ethtool -i eth0
driver: igc
version: 5.15.46-Unraid
firmware-version: 1057:8754
expansion-rom-version: 
bus-info: 0000:07:00.0
...

# echo "auto" > /sys/bus/pci/devices/0000:07:00.0/power/control

# ethtool -i eth0
... no reaction, server is dead, same happens if network settings are changed through Unraid WebGUI

     

    In Ubuntu it can be changed from "auto" to "on" and vice versa without problems: 

    # echo "auto" > /sys/bus/pci/devices/0000:07:00.0/power/control

# ethtool enp7s0
Settings for enp7s0:
Cannot get device settings: No such device

# echo "on" > /sys/bus/pci/devices/0000:07:00.0/power/control

# ethtool -i enp7s0
driver: igc
version: 0.0.1-k
firmware-version:
expansion-rom-version:
bus-info: 0000:07:00.0
...

     

    Note: Executing "powertop --auto-tune" does the same and as many users use powertop to save energy, they will probably  suffer from the same bug.

    • Upvote 1
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    RedReddington

    I also came around this issue.

    Somehow it was working fine with "--auto-tune" for half a year now, but I noticed some crashes after the recent updates and finally found this information.

    I manually set all my PCI devices to auto and left the built-in NIC as is.
    Maybe I will just disable it in the BIOS, but I noticed some weird bug that I can't reach lower C-states when I disabled it.

    Atleast when I was testing it a while ago...
     

    Does this issue only apply for unused NICs?

    I also have a Intel 710-DA4 on one of my chipset NVME slots with a PCIe converter.

     

    I can also finally reach C10 states after using that PCIe converter (I was using a native PCIe lane from the CPU lane and could only reach C3).

     

    But now the power consumption is the same, which is weird.

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  • Status Definitions

     

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