CPU usage with Cake QoS on GT-AX6000 when copying files over Wifi

[xcvb]

On my GT-AX6000 with Asuswrt-Merlin firmware installed and Cake QoS enabled, I notice that CPU usage on 1 core is 100% when copying files over Wifi (from a Windows SMB share to a laptop).

With the laptop connected at 2401/2401Mbps I`m getting around 100MB/s with Cake QoS enabled. With Cake disabled, I`m getting 112MB/s, basically maximizing the 1Gbit LAN connection, with almost no CPU usage.

Not sure why Cake need to be active and/or analyze bandwidth usage over LAN? Anybody else having this issue? Also I can`t remember this being a problem on my previous setup with AX88U.

 

[dave14305]

Cake is not the issue, since it only monitors the WAN traffic. The issue must be that Cake requires all the fancy HW acceleration to be disabled in order to do its job.

Run your test again with Cake disabled. Then run it again after running these commands:

runner disable
fc disable
fc flush

Hopefully, you get same same poor performance as when Cake is enabled, only it’s disabled now. But the acceleration is gone.

Reenable it with:

runner enable
fc enable

 

[Crimliar]

On a 1Gbps WAN setup, Cake is not really required anyways!

 

[xcvb]

Cake is not the issue, since it only monitors the WAN traffic. The issue must be that Cake requires all the fancy HW acceleration to be disabled in order to do its job.

Run your test again with Cake disabled. Then run it again after running these commands:

runner disable
fc disable
fc flush

Hopefully, you get same same poor performance as when Cake is enabled, only it’s disabled now. But the acceleration is gone.

Reenable it with:

runner enable
fc enable

You are right, it was because HW acceleration is disabled when Cake is enabled. But still seems like poor performance even with acceleration disabled. Shouldn`t the CPU in todays routers be powerful enough to transfer files as 1Gbps?

And just to clarify, the 1Gbps connection was to the network share on the local network, not WAN. WAN connection is 300Mbps (fiber).

 

[Tech9]

Shouldn`t the CPU in todays routers be powerful enough to transfer files as 1Gbps?

This router's CPU can process about 400Mbps WAN-LAN with no NAT acceleration, but why is this affecting your local transfers is not very clear. I remember seeing reports about similar side effect on RT-AX86U model. The speed difference you see is not critical, just use whatever works best as a balance between the type of QoS you need and acceptable local transfer speeds.

 

[xcvb]

With Cake enabled and set to 300Mbps, the CPU usage is 99% on one core when downloading a file at max speed (300Mbps). This also affects Wifi-LAN performance, I`m getting like 2-10MB/s over Wifi-LAN while downloading due to HW acceleration being disabled.

Strange that the load isn`t balanced between the cores. The CPU in this router also seems weak.

 

[Tech9]

Strange at the load isn`t balanced between the cores.

Single threaded processes run on one CPU core.

If this is strange for you - your router with 64-bit CPU runs on 32-bit OS.

 

[xcvb]

Single threaded processes run on one CPU core.

I assume traffic on Wifi-LAN and traffic on WAN-LAN are separate processes/threads and could potentially run on separate cores? Right now it seems that "everything" is executed on the same core. Even the web GUI becomes slow when number one core usage is at 99%

 

[dave14305]

I assume traffic on Wifi-LAN and traffic on WAN-LAN are separate processes/threads and could potentially run on separate cores?

Login via SSH and run this command while you run a speed test:

watch cat /proc/interrupts

You should see a lot of activity on CPU0. Ctrl-C to exit the command.