RE: [PATCH 3/3] net: usb: cdc_ncm: don't spew notifications

Grant Grundler [off-list ref]

Sent: Tuesday, January 19, 2021 6:03 AM
Subject: Re: [PATCH 3/3] net: usb: cdc_ncm: don't spew notifications

[...]

quoted

RTL8156 sends notifications about every 32ms.
Only display/log notifications when something changes.

This issue has been reported by others:
        https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1832472
        https://lkml.org/lkml/2020/8/27/1083

...
[785962.779840] usb 1-1: new high-speed USB device number 5 using

xhci_hcd

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[785962.929944] usb 1-1: New USB device found, idVendor=0bda,

idProduct=8156, bcdDevice=30.00

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[785962.929949] usb 1-1: New USB device strings: Mfr=1, Product=2,

SerialNumber=6

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[785962.929952] usb 1-1: Product: USB 10/100/1G/2.5G LAN
[785962.929954] usb 1-1: Manufacturer: Realtek
[785962.929956] usb 1-1: SerialNumber: 000000001
[785962.991755] usbcore: registered new interface driver cdc_ether
[785963.017068] cdc_ncm 1-1:2.0: MAC-Address: 00:24:27:88:08:15
[785963.017072] cdc_ncm 1-1:2.0: setting rx_max = 16384
[785963.017169] cdc_ncm 1-1:2.0: setting tx_max = 16384
[785963.017682] cdc_ncm 1-1:2.0 usb0: register 'cdc_ncm' at

usb-0000:00:14.0-1, CDC NCM, 00:24:27:88:08:15

quoted

[785963.019211] usbcore: registered new interface driver cdc_ncm
[785963.023856] usbcore: registered new interface driver cdc_wdm
[785963.025461] usbcore: registered new interface driver cdc_mbim
[785963.038824] cdc_ncm 1-1:2.0 enx002427880815: renamed from usb0
[785963.089586] cdc_ncm 1-1:2.0 enx002427880815: network connection:

disconnected

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[785963.121673] cdc_ncm 1-1:2.0 enx002427880815: network connection:

disconnected

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[785963.153682] cdc_ncm 1-1:2.0 enx002427880815: network connection:

disconnected

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...

This is about 2KB per second and will overwrite all contents of a 1MB
dmesg buffer in under 10 minutes rendering them useless for debugging
many kernel problems.

This is also an extra 180 MB/day in /var/logs (or 1GB per week) rendering
the majority of those logs useless too.

When the link is up (expected state), spew amount is >2x higher:
...
[786139.600992] cdc_ncm 2-1:2.0 enx002427880815: network connection:

connected

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[786139.632997] cdc_ncm 2-1:2.0 enx002427880815: 2500 mbit/s downlink

2500 mbit/s uplink

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[786139.665097] cdc_ncm 2-1:2.0 enx002427880815: network connection:

connected

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[786139.697100] cdc_ncm 2-1:2.0 enx002427880815: 2500 mbit/s downlink

2500 mbit/s uplink

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[786139.729094] cdc_ncm 2-1:2.0 enx002427880815: network connection:

connected

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[786139.761108] cdc_ncm 2-1:2.0 enx002427880815: 2500 mbit/s downlink

2500 mbit/s uplink

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...

Chrome OS cannot support RTL8156 until this is fixed.

Signed-off-by: Grant Grundler <redacted>

Reviewed-by: Hayes Wang <redacted>

Best Regards,
Hayes