Hi Dirk,
On Tue, Aug 11, 2020 at 12:58:15PM +0200, Dirk Kostrewa wrote:
> Hi Salavatore,
>
> as an additional control, I have completely uninstalled the nvidia graphics
> driver and repeated the kworker observations using the nouveau graphics
> driver with the kernel 4.19.0-10-amd64. This time, there are even two
> kworker processes constantly running with high CPU load:
>
> $ top
> top - 12:37:20 up 10 min, 4 users, load average: 2.79, 2.54, 1.56
> Tasks: 197 total, 3 running, 194 sleeping, 0 stopped, 0 zombie
> %Cpu(s): 0.0 us, 24.2 sy, 0.0 ni, 74.2 id, 0.0 wa, 0.0 hi, 1.6 si, 0.0
> st
> MiB Mem : 15889.4 total, 13964.7 free, 626.8 used, 1297.9 buff/cache
> MiB Swap: 0.0 total, 0.0 free, 0.0 used. 14849.1 avail Mem
>
> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
> 164 root 20 0 0 0 0 R 80.0 0.0 8:41.67
> kworker/6:2+pm
> 455 root 20 0 0 0 0 R 80.0 0.0 8:28.23
> kworker/2:2+pm
> 22 root 20 0 0 0 0 S 20.0 0.0 2:14.82
> ksoftirqd/2
> 42 root 20 0 0 0 0 S 20.0 0.0 2:08.67
> ksoftirqd/6
> 1 root 20 0 169644 10212 7796 S 0.0 0.1 0:01.52 systemd
> 2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd
> 3 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 rcu_gp
> 4 root 0 -20 0 0 0 I 0.0 0.0 0:00.00
> rcu_par_gp
> 6 root 0 -20 0 0 0 I 0.0 0.0 0:00.00
> kworker/0:0H-kblockd
> 7 root 20 0 0 0 0 I 0.0 0.0 0:00.05
> kworker/u16:0-event+
>
> The stacks of the two kworker processes show the same output:
>
> [<0>] 0xffffffffffffffff
>
> I have appended the top 5000 lines tracing as a compressed ascii file
> out-cut.txt,gz and the dmesg output as compressed ascii file dmesg.txt.gz.
>
> I hope, this helps to find out where the problem with the high CPU load of
> the kworker processes come from.
Thanks this is very helpful.
I suspect what you are seeing is an issue with the usb hubport present
before but now uncovered due to the upstream change e9fb08d617bf
("xhci: prevent bus suspend if a roothub port detected a over-current
condition")[1], which was as well backported to v4.19.y in 4.19.119.
Can you add some dynamic debugging on the 'drivers/usb/'[2] ideally at
boot time. On runtime it is
# echo 'file drivers/usb/* +p;' > /sys/kernel/debug/dynamic_debug/control
or as kernel parameter to have enable the debug messages at boot time
already:
dyndbg="file drivers/usb/* +p;"
Can you attach the dmesg with the enabled debugging?
Regards,
Salvatore
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e9fb08d617bfae5471d902112667d0eeb9dee3c4
[2] https://www.kernel.org/doc/html/latest/admin-guide/dynamic-debug-howto.html
