* Thomas Gleixner | 2015-08-04 14:05:10 [+0200]:
>On Tue, 4 Aug 2015, Nicholas Mc Guire wrote:
>> <snip>
>> 3 root -2 0 0 0 0 R 60.3 0.0 5756:16
>> ksoftirqd/0
>> 23 root -2 0 0 0 0 R 50.8 0.0 4948:08
>> ksoftirqd/2
>> 17 root -2 0 0 0 0 S 50.6 0.0 4897:13
>> ksoftirqd/1
>> 29 root -2 0 0 0 0 S 50.4 0.0 4953:24
>> ksoftirqd/3
>
>So ksoftirqd eats 50+% CPU on each core. On an idle system!?! Any
>chance that you can get a function trace snapshot out of it?
This might be a .config thing, device driver or user land behaviour.
Usually ksoftirqd should remain (almost) idle because most of BH work
remains in task-context and not in ksoftirqd. tasklets for instance
should run in ksoftirqd. So a function trace or event tracing to figure
out what is scheduling the softirq might give a pointer.
I have here a AMD box with
3 root -2 0 0 0 0 S 1.3 0.0 126:16.31 ksoftirqd/0
18 root -2 0 0 0 0 S 1.3 0.0 136:55.85 ksoftirqd/1
30 root -2 0 0 0 0 S 1.3 0.0 138:50.52 ksoftirqd/3
24 root -2 0 0 0 0 S 1.0 0.0 143:54.28 ksoftirqd/2
with a 15 days uptime. That one percent CPU usage on a idle system looks
odd here, too.
>Thanks,
>
> tglx
Sebastian
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