On Ubuntu 16.04 computer I saw kworker
take up 80% of a CPU, consistently.
I generated a perf report:
sudo apt-get install linux-tools-common linux-tools-$(uname -r)
- Record some 10 seconds of backtraces on all CPUs
sudo perf record -g -a sleep 10
- View it with
sudo perf report
.
Top few results are:
Samples: 47K of event 'cycles:ppp', Event count (approx.): 38282161158
Children Self Command Shared Object Symbol
+ 77.04% 0.00% kworker/3:3 [kernel.kallsyms] [k] ret_from_fork
+ 77.04% 0.00% kworker/3:3 [kernel.kallsyms] [k] kthread
+ 77.04% 0.00% kworker/3:3 [kernel.kallsyms] [k] worker_thread
+ 77.00% 0.13% kworker/3:3 [kernel.kallsyms] [k] process_one_work
+ 76.26% 0.04% kworker/3:3 [kernel.kallsyms] [k] rpm_idle
+ 75.98% 0.06% kworker/3:3 [kernel.kallsyms] [k] rpm_suspend
+ 75.97% 0.03% kworker/3:3 [kernel.kallsyms] [k] pm_runtime_work
+ 75.84% 0.03% kworker/3:3 [kernel.kallsyms] [k] __rpm_callback
+ 75.82% 0.01% kworker/3:3 [kernel.kallsyms] [k] usb_runtime_idle
+ 75.76% 0.00% kworker/3:3 [kernel.kallsyms] [k] __pm_runtime_suspend
+ 75.64% 0.00% kworker/3:3 [kernel.kallsyms] [k] rpm_callback
+ 75.61% 0.04% kworker/3:3 [kernel.kallsyms] [k] usb_runtime_suspend
+ 75.51% 0.03% kworker/3:3 [kernel.kallsyms] [k] usb_suspend_both
+ 73.51% 0.15% kworker/3:3 [kernel.kallsyms] [k] usb_control_msg
+ 71.97% 0.14% kworker/3:3 [kernel.kallsyms] [k] usb_start_wait_urb
+ 68.38% 0.05% kworker/3:3 [kernel.kallsyms] [k] usb_submit_urb
+ 68.33% 0.30% kworker/3:3 [kernel.kallsyms] [k] usb_submit_urb.part.8
+ 67.75% 0.82% kworker/3:3 [kernel.kallsyms] [k] usb_hcd_submit_urb
+ 60.96% 60.41% kworker/3:3 [kernel.kallsyms] [k] xhci_hub_control
+ 55.99% 0.12% kworker/3:3 [kernel.kallsyms] [k] hub_suspend
+ 54.97% 0.04% kworker/3:3 [kernel.kallsyms] [k] set_port_feature
+ 19.36% 0.01% kworker/3:3 [kernel.kallsyms] [k] usb_resume_interface.isra.8
+ 19.35% 0.02% kworker/3:3 [kernel.kallsyms] [k] hub_resume
+ 19.32% 0.14% kworker/3:3 [kernel.kallsyms] [k] hub_activate
+ 18.78% 0.08% kworker/3:3 [kernel.kallsyms] [k] hub_ext_port_status
+ 11.13% 0.00% ksoftirqd/3 [kernel.kallsyms] [k] ret_from_fork
+ 11.13% 0.00% ksoftirqd/3 [kernel.kallsyms] [k] kthread
+ 10.44% 0.51% ksoftirqd/3 [kernel.kallsyms] [k] smpboot_thread_fn
I do not know how to reproduce. It goes away after a reboot.
What is going on?
Best Answer
Same problem here on a Dell XPS laptop and kernel 4.4.0-130
I fixed it by disabling dynamic USB power management in kernel
I added
usbcore.autosuspend=-1
to my kernel's boot command line:To do that permanently, open the grub configuration file
and add the flag described above.
Next you have to update your grub via
After reboot, everything should be fine, the busy CPU is now free for doing something useful :)
Disabling dynamic PM might impact battery life when you have USB devices connected, but few USB devices are able to handle this mode....