Very high ksoftirqd usage on Netgear R7800

Since I upgraded to 18.06.2 (just after it came out) I've had periods ksoftirqd would run very high load. It's a stock R7800 with one extra package installed (openssh-sftp-server 7.7p1-1) with a fairly low-end internet traffic (the device is behind a 45Mbit/s connection).

I did a full reinstall without retaining settings and without restoring an old backup but the problem persists. Any idea what could be the problem?


OpenWrt_Processes

I get a sense it has something to do with the wireless driver for one of the radios. When ksoftirqd is maxed out Radio0 is essentially non-functioning. It usually has at least a number of devices associated with it, the rest using Radio1, but not while ksoftirqd is playing up.

When I try to restart wireless for Radio0 the whole router crashes and restarts. Afterwards the ksoftirqd issue has gone and Radio0 is functioning again, at least for a while...

Are there known issues with the driver for the Qualcomm Atheros QCA9984 802.11ac radio?

https://forum.openwrt.org/search?q=ath10k%20issues%20R7800%20order%3Alatest_topic

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Thanks, I had seen some of those but considering I had no issues under 18.06.1 (and still have no issues on another R7800 that I kept on 18.06.1), and the problems didn't surface until an update to 18.06.2, I had assumed that the ath10K issues were related to Master, not to Release.

On the advice in one of those topics I have switched the ac radio to use 20 MHz channel width and haven't had any problems for a week now. It limits the speed on the ac channel to 144 Mbit/s but considering my DSL is only 80 Mbit/s down that is no major issue at the moment.

I'll keep an eye on developments with the ath10K driver.