Discussion:
[BUG report] kworker issue on A20 SoC with kernel >= 4.12.0
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Kai
2017-12-28 04:45:00 UTC
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Hardware: cubieboard2, cubietruck, Banana Pi
OS: Armbian, Archlinux with kernel >= 4.12.0 (4.12.x, 4.13.x, 4.14.x)
SoC: A20

Issue description: top shows that kworker constantly eats 8%~13% CPU,
performance sensitive apps run stuttered, comparing to they behave on
4.11.x.

I'm using cb2&ct with archlinux, Banana Pi & Armbian are reported on
Armbian forum, the common ground is A20 SoC, kernels later than 4.12.0,
considered to be a thermal sensor polling related BUG.
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Sebastien Lucas
2017-12-29 08:17:07 UTC
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Hi,

I also have the same problem with a Banana Pi (the very old first one) and
Armbian with kernel 4.13.16-sunxi.

I tried to debug a little and run those lines :

$ echo workqueue:workqueue_queue_work > /sys/kernel/debug/tracing/set_event
$ cat /sys/kernel/debug/tracing/trace_pipe > out.txt
(wait a few secs)
$ grep "10975" out.txt


I got this output : https://pastebin.com/t7Z2e9g0

I see a lot of gc_worker [nf_conntrack] so I'm not sure it's related to the
thermal sensor, imho it's related to network.

I've not tried to connect a serial console and disable all network to see
if that fix the problem. I might do that this weekend if I have some time.

Thanks in advance.
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Kai
2018-01-30 08:58:36 UTC
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It's getting even worse after upgraded to kernel 4.15.0, another kworker
process eats around 35% CPU every 10 secs.


圚 2017幎12月29日星期五 UTC+8䞊午2:04:40Kai写道
Post by Kai
Hardware: cubieboard2, cubietruck, Banana Pi
OS: Armbian, Archlinux with kernel >= 4.12.0 (4.12.x, 4.13.x, 4.14.x)
SoC: A20
Issue description: top shows that kworker constantly eats 8%~13% CPU,
performance sensitive apps run stuttered, comparing to they behave on
4.11.x.
I'm using cb2&ct with archlinux, Banana Pi & Armbian are reported on
Armbian forum, the common ground is A20 SoC, kernels later than 4.12.0,
considered to be a thermal sensor polling related BUG.
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Kai
2018-04-27 09:16:00 UTC
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PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+
COMMAND
196 root 20 0 0 0 0 I 16.6 0.0 0:12.59
kworker/0+
110 root 20 0 0 0 0 I 6.6 0.0 0:22.28
kworker/1+
433 root 20 0 8996 3392 2920 R 1.0 0.3 0:00.73
top
...

On 4.16.4 .
I'm not able to debug it myself for now, however, A20 was abandoned by
everyone?

圚 2018幎1月30日星期二 UTC+8䞋午4:58:37Kai写道
Post by Kai
It's getting even worse after upgraded to kernel 4.15.0, another kworker
process eats around 35% CPU every 10 secs.
圚 2017幎12月29日星期五 UTC+8䞊午2:04:40Kai写道
Post by Kai
Hardware: cubieboard2, cubietruck, Banana Pi
OS: Armbian, Archlinux with kernel >= 4.12.0 (4.12.x, 4.13.x, 4.14.x)
SoC: A20
Issue description: top shows that kworker constantly eats 8%~13% CPU,
performance sensitive apps run stuttered, comparing to they behave on
4.11.x.
I'm using cb2&ct with archlinux, Banana Pi & Armbian are reported on
Armbian forum, the common ground is A20 SoC, kernels later than 4.12.0,
considered to be a thermal sensor polling related BUG.
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Timo S.
2018-05-28 13:55:39 UTC
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<snip>
On 4.16.4 .
I'm not able to debug it myself for now, however, A20 was abandoned by
everyone?
I don't think A20 was abandond - at least not when it comes to using the
devices. Development might be stalled since Linux support is mostly feature
complete, though.

I can't test your issue as I'm using plain Debian with an older Linux
kernel 4.9.x on my A20 devices. But for debugging, I would suggest to start
with a vanilla kernel build. Armbians kernel caries quite a few patches
(+100), so you can't be sure whether your issue comes from these patches or
whether all users of a mainline kernel are affected.
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Stefan Monnier
2018-05-30 00:43:43 UTC
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Post by Timo S.
I don't think A20 was abandond - at least not when it comes to using the
devices.
Indeed, definitely not:
It's still prominently listed at https://wiki.debian.org/CheapServerBoxHardware

I think nowadays the ESPRESSObin provides a better option, but the A20
boxes are still a competitive alternative.


Stefan
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Vincent Legoll
2018-05-30 07:46:05 UTC
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Hello,

On Wed, May 30, 2018 at 2:43 AM, Stefan Monnier
Post by Stefan Monnier
Post by Timo S.
I don't think A20 was abandond - at least not when it comes to using the
devices.
It's still prominently listed at https://wiki.debian.org/CheapServerBoxHardware
And then there is the upcoming EOMA68 boards
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Vincent Legoll
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