[arch-general] Help diagnosing kworker 'bug'

[Oon-Ee Ng]

On Wed, Aug 6, 2014 at 3:43 PM, Oon-Ee Ng <ngoonee.talk at gmail.com> wrote:
> On Wed, Aug 6, 2014 at 10:40 AM, Anatol Pomozov
> <anatol.pomozov at gmail.com> wrote:
>> 'perf' is a great and very powerful tool that allow to debug problems
>> like this. Run '# perf top -g -p $PID' and it will show where the
>> process spends *cpu cycles*. It should be enough to understand what
>> kworker thread does. For all curious minds I highly recommend to read
>> this tutorial https://perf.wiki.kernel.org/index.php/Tutorial
>
> Thanks, if my boy gets to sleep early tonight I'll do that.

Having tried that out, I don't really understand the output. It seems
the first column is CPU usage and the second is...? IO?

Anyway these are the top 3 things in my output after a short amount of
time. Other things which are low in CPU usage and high in the second
column are find_next_zero_bit and _raw_spin_lock. Not sure what I
should glean from this.
+   17.74%     0.10%  [kernel]          [k] __filemap_fdatawrite_range
+   15.04%     0.02%  [kernel]          [k] filemap_fdatawrite_range
+    9.93%     9.93%  [kernel]          [k] find_next_bit