Solved AC88U 100% CPU while downloading with HW Acceleration Enabled

Ersan

Occasional Visitor
I swear this used to work fine before, but since at least a couple versions ago my AC88U started using 100% of one core while downloading preventing me from using the full gigabit internet I have. On Steam especially it will not go over 30MB/s and while it's downloading the rest of the network starts dropping packets, having inconsistent ping response times, and websites will stop loading. Torrents and single-threaded HTTP downloads will still run at close to 1gbit, but again with the 100% CPU and severe network instability.

The Sysinfo page says HW Acceleration is enabled and Switch control says CTF is enabled. Adaptive QoS, Traffic Analyzer, Game Accelerator, AiProtection are all off. The only things running are an OpenVPN server, afpd (Time Machine), some URL filters, and a program called VirtualHere on the jffs - I tried disabling all of these and it didn't fix the problem. top says one core is at 100% sirq while I'm downloading.

I tried factory resetting the router and then restoring the settings I had saved but that didn't fix it, I'm not especially looking forward to redoing all of the settings from scratch but if that's what I have to do I will. Next step is to try factory resetting without restoring settings and seeing if that fixes it, but I figured I would ask here first and see if anyone had any ideas before I go through that long process.
 

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ColinTaylor

Part of the Furniture
Try killing the vhusbdarm process and seeing if that makes a difference as that is also consuming a lot of CPU.
 

Ersan

Occasional Visitor
Try killing the vhusbdarm process and seeing if that makes a difference as that is also consuming a lot of CPU.
I did, no dice - and it only uses CPU when the USB device is being used (it was in the screenshot, an xbox controller)
 

Ersan

Occasional Visitor
The only unusual thing about my setup that comes to mind is that my ISP (CenturyLink) requires a tagged VLAN (ID 201) to communicate with the ONT so I have that set in LAN -> IPTV. Maybe that's CPU bound in more recent firmwares but wasn't before for some reason?

I think I'm actually going to try to downgrade to an earlier firmware next.

EDIT: Downgrading didn't fix it, but factory resetting the router did. As soon as I restore my settings backup it breaks again. I guess now I have to go through every setting and see if I can't figure out what's wrong.
 

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Ersan

Occasional Visitor
Solved:
It was the URL Filter, when it is disabled this issue does not occur (it still shows 100% CPU usage on one core while downloading but the speed and network are unaffected). I didn't realize this initially because just disabling it once it has been enabled doesn't fix the problem, I have to completely reboot the router with URL filter disabled before the problem goes away.

I added the entries to dnsmasq.conf instead, which is suitable for my needs.
 
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