[solved] kworker runs on 30%

[musv]

Hi there,

I just noticed, that one kworker process runs constantly on 30% of cpu last.

top tells me:

[tholin]

My solution might not be the best but it works.

You can use kernel tracing to find out what that kworker is doing. Run "echo "workqueue:workqueue_queue_work" > /sys/kernel/debug/tracing/set_event" and then grep /sys/kernel/debug/tracing/trace for the pid of the kworker. In your example 82. This assumes that the debugfs is mounted and the kernel is compiled with support for tracing.
You should get a line like:

kworker/0:1-82 [000] d..2 5427.299626: workqueue_queue_work: work struct=ffff88033ad992d0 function=kcryptd_crypt workqueue=ffff88041bcd3400 req_cpu=8 cpu=4294967295

Here we see that on my system kworker/0:1 with pid 82 ran the kernel function "kcryptd_crypt". So we know that kworker/0:1 is doing work related to cryptography (dm-crypt).
Sometimes the function you get has a none descriptive name like "function=do_worker". Then you have to grep the kernel source to find out what that is.
drivers/md/dm-thin.c got the line INIT_WORK(&pool->worker, do_worker); and that is the only use of do_worker so the kworker calling do_worker is doing work related to dm-thin.

Once you found what kernel code is executed you have to manually check menuconfig for something that disables that code.

[musv]

Thanks, I'll keep this in my mind.

Until now there's no /sys/kernel/debug/tracing folder. I guess, I have to add some tracing support into the kernel config.

Nevertheless I found the error by brute force methode of recompiling the kernel again and again.

I have 2 soundcards in my computer - a Asus Xonar DS and an internal HDA Intel. I'm using the same sound card config already for about 4 years. The problem I notice since 4.8.7.