Comment 10 for bug 1425803

Kernel 4.0-rc2 tested. Problem remains.

In rc2 there was a minimal fglrx driver in the kernel so I was able to get a more usual desktop and use the graphical system monitor app. The manifestation of the problem is slightly different now. Total CPU usage still goes to 24 - 25% when a USB 3.0 hub is plugged in, but the khubd process does not seem to take excessive CPU time. Instead, the kworker and ksoftirqd processes take it all up. The kworker thread(s) take in total about 17% and the ksoftirqd thread(s) about 7%.

The problem remains the same in all other aspects. It is present with hubs using the VIA or Genesyslogic chipsets. Excessive CPU usage continues even after the external hubs are disconnected. The cure remains to unbind and then bind the xhci_hcd driver serving the internal USB 3.0 hub.