[sles-beta] Tasks get stuck with RT priority

[Uwe Drechsel]

On Wed, Apr 30, Indika Prasad Kumara wrote:

> Hi all,
> 
> I have a X3650 M4 (16core 64GB RAM....). After fresh installation of
> SLES12, I run following command (as root).
> 
> taskset -c 2 chrt 99 ./stress -c 1
> 
> this command will run the stress binary on CPU 2 with RT priority.
> stress -c 1 will spawn one thread that does a while(true); - endless
> loop, taking 100% CPU.
> 
> Note that there are 15 other CPUs free, after 10 ~ 15 seconds, we can
> see couple of kworkers come and hang in "R" state on CPU 2.
> 
> I know running 100% with RT priority is considered bad, but here I'm
> running a controlled setup, which one thread runs with pure CPU bound
> load. Why are kworkers get scheduled on this core when there are 15
> other free cores available ?
> 

This is a well known issue for upstream kernel developers, no ETA
available yet.


Uwe 

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   Someone who believes imaginary things appear right before your i's.