I upgraded again to the latest. This time I did a factory reset after the upgrade and the CPU utilization went back to normal.
Hmm, makes me wonder if I should do it. I'm not super worried about Krook vuln and I have a backup of the config. Did you restore from .CFG backup after factory reset?
If I wish to go back to the previous firmware, is it ok to just download the previous version and flash the router?
That's what I did. I manually downloaded and applied the previous firmware and my router is back to normal. 99.9% there's no need to factory reset after firmware upgrade. No one designs a product with that intent built into it or it (or the company) would not be on the market for long. Only in the really rare occasion where things go sideways and even reverting doesn't work is it better to start from scratch. It's just so odd that some folks have no issue after firmware upgrade and some do. I've not factory reset my router since I bought it. All firmware upgrades worked fine save for this one. And to me it's not worth a factory reset to fix the CPU bug.
We all know and love Asus and I bet they're investigating the issue and will push a fix in short order.
ASUS recommends that you try the Hard Factory Reset before attempting any advanced troubleshooting.
https://www.asus.com/US/support/FAQ/1039074
But I suppose downgrading firmware is not advanced troubleshooting.
OE
Yes of course. And like Microsoft, if their patch screws something up, uninstalling the patch usually fixes it. Still, this is obviously a bug in the firmware (for some) if reverting fixes it.
I was also getting 100% cpu usage on 385.20253, mostly by [mtdblock3] according to top. I saw that there was a new directory in /jffs called asd, and removing that directory immediately resolved the problem.
When the asd process restarts, /jffs/asd is recreated and the cpu goes to 100% again. A persistent fix is to use touch /jffs/asd to make a file that blocks creation of the directory.
Well, the apparent "fix" of a Factory Reset that I thought had worked, didn't work for long as the persistant CPU utilization was back up to >85% when I checked it a day later. I reverted to 3.0.0.4.385.20252 and all is fine CPU wise again. I will try a Hard Factory Reset after the next upgrade, but doubt that will work. If not, I will recomplain on the Feedback to ASUS and try aaronk's workaround.I upgraded again to the latest. This time I did a factory reset after the upgrade and the CPU utilization went back to normal.
Well, tried the hard factory reset, and it looked okay for a day, then last night it obviously went back up to > 90% utilization no matter what, and is staying up there. As aaronk pointed out, most of the cpu usage is by [mtdblock3]. Submitted another feedback to ASUS.Well, the apparent "fix" of a Factory Reset that I thought had worked, didn't work for long as the persistant CPU utilization was back up to >85% when I checked it a day later. I reverted to 3.0.0.4.385.20252 and all is fine CPU wise again. I will try a Hard Factory Reset after the next upgrade, but doubt that will work. If not, I will recomplain on the Feedback to ASUS and try aaronk's workaround.
Not that this helps those who run 68U's as their primary routers, but none of my (4) four 68U's running as AiMesh nodes have high CPU usage on the 3.0.0.4.385_20253-gb338b0e firmware release. All four are below 2-4% CPU on average, though the only way I have of knowing CPU usage on any of them is to SSH in and run "top" to see it. From what I've seen of the "high CPU usage" bugs in the past, the httpd/httpds process is the culprit (the process that runs the web UI for the router). The httpds process does not run however on AiMesh nodes for obvious reasons.
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