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

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Date:   Tue, 19 Jan 2021 01:23:15 +0000
From:   Hayes Wang <hayeswang@...ltek.com>
To:     Grant Grundler <grundler@...omium.org>,
        nic_swsd <nic_swsd@...ltek.com>
CC:     Oliver Neukum <oliver@...kum.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 3/3] net: usb: cdc_ncm: don't spew notifications

Grant Grundler <grundler@...omium.org>
> Sent: Tuesday, January 19, 2021 6:03 AM
> Subject: Re: [PATCH 3/3] 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@...omium.org>

Reviewed-by: Hayes Wang <hayeswang@...ltek.com>

Best Regards,
Hayes