Arch Linux

Ultraman

Member

Registered: 2009-12-24

Posts: 242

Re: 2.6.37 Still suffering from high load

I found a way to stop the kworker crazyness and to start it again on a running system.
In my case it seems to be connected to a USB issue.

When my kworker thread is demanding 70% CPU I unload the USB modules: uhci_hcd and ehci_hcd
After doing so kworker stops eating my CPU alive and all is well.

After that I load ehci_hcd and uhci_hcd again, in that order. All is still OK.
But then I plug in a USB device, in this case a USB stick (tried 2 different ones, same result) and kworker is back up there again using up ~70% CPU.
Unplugging the USB device does not resolve the issue, I need to unload the modules again.
And then I can rinse and repeat.

I'm going to see if I can reproduce this when booting from battery.
And I have a feeling it might be related to USB auto suspend over here, but I have no proof of this yet.

Ultraman

Member

Registered: 2009-12-24

Posts: 242

Re: 2.6.37 Still suffering from high load

I was able to reproduce, so that is a workaround for me. But really more of a band-aid than a solution.
Because even after disabling usb auto-suspend in my configuration files and disabling it on boot by echoing -1 to /sys/module/usbcore/parameters/autosuspend did not help. After plugging in a USB stick kworker woke up to start thrashing again.
And I had to unload the modules again to make it stop.

So I continued the hunt and came across a bug report about high load averages on RedHat: here
They talked about PCIE ASPM modes, and I remember that those power saving features were also included in the ARCH kernel pretty recently, around .35/.36 I believe. So I decided to give their suggestion of adding "pcie_ports=compat" to my bootline a go.
And this seems to have solved my issue. I can now boot off battery power and not have kworker thrash my CPU for attention.
I've yet to plug in any USB devices tho, so I'm still unsure whether that works OK now as well, but at least I can boot without issues now and I know how to stop this so my battery life gets back to acceptable levels.

Hope this helps you!