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

[Hayes Wang]

Grant Grundler <grundler@xxxxxxxxxxxx>
> Sent: Wednesday, January 20, 2021 9:12 AM
> Subject: [PATCH net] net: usb: cdc_ncm: don't spew notifications
> 
> 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
> [785962.929944] usb 1-1: New USB device found, idVendor=0bda,
> idProduct=8156, bcdDevice=30.00
> [785962.929949] usb 1-1: New USB device strings: Mfr=1, Product=2,
> SerialNumber=6
> [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
> [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
> [785963.121673] cdc_ncm 1-1:2.0 enx002427880815: network connection:
> disconnected
> [785963.153682] cdc_ncm 1-1:2.0 enx002427880815: network connection:
> disconnected
> ...
> 
> 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
> [786139.632997] cdc_ncm 2-1:2.0 enx002427880815: 2500 mbit/s downlink
> 2500 mbit/s uplink
> [786139.665097] cdc_ncm 2-1:2.0 enx002427880815: network connection:
> connected
> [786139.697100] cdc_ncm 2-1:2.0 enx002427880815: 2500 mbit/s downlink
> 2500 mbit/s uplink
> [786139.729094] cdc_ncm 2-1:2.0 enx002427880815: network connection:
> connected
> [786139.761108] cdc_ncm 2-1:2.0 enx002427880815: 2500 mbit/s downlink
> 2500 mbit/s uplink
> ...
> 
> Chrome OS cannot support RTL8156 until this is fixed.
> 
> Signed-off-by: Grant Grundler <grundler@xxxxxxxxxxxx>

Reviewed-by: Hayes Wang <hayeswang@xxxxxxxxxxx>

Best Regards,
Hayes