Hi Salvatore,yesterday, I installed the kernel 5.6.0 from the Buster Backports and saw again a kworker process with high CPU load. Oddly, this morning, my laptop didn't boot, so I decided to do a fresh install of Debian Buster 10.5.0 (image with non-free firmware because of my wifi card) and installed only thunderbird and vim. There is still one kworker process with permanently high CPU load.
I gave the dyndbg command that you told me as a kernel parameter upon booting and have appended the dmesg output as file dmesg.txt.gz.
Cheers, Dirk. Am 11.08.20 um 21:21 schrieb Salvatore Bonaccorso:
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
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