[BUG?] Possible scheduler bug on Rock 5B RK3588 on 7.2.5

[Chaoyi Chen]

On 9/18/2026 3:15 AM, No SPAM here wrote:
> Hi
> 
> On Thursday, 17 September 2026 at 03:37, Chaoyi Chen <chaoyi.chen at rock-chips.com> wrote:
> 
>> Hello Trevor,
>>
>> On 9/17/2026 9:21 AM, No SPAM here wrote:
>>>> Would you mind trying to disable `CONFIG_SCHED_CLUSTER` and checking whether
>>>> the problem still reproduces?
> 
> trevor at rock-5b:~$ uname -a
> Linux rock-5b 6.18.52-current-rockchip64 #1 SMP PREEMPT Mon Sep 14 11:36:19 UTC 2026 aarch64 GNU/Linux
> trevor at rock-5b:~$ grep CONFIG_SCHED_CLU /boot/config-6.18.52-current-rockchip64 
> # CONFIG_SCHED_CLUSTER is not set
> trevor at rock-5b:~$ sar | tail -5
> 
> 18:50:15        CPU     %user     %nice   %system   %iowait    %steal     %idle
> 19:00:15        all     99.89      0.00      0.11      0.00      0.00      0.00
> 19:10:15        all     99.89      0.00      0.11      0.00      0.00      0.00
> Average:        all     99.89      0.00      0.11      0.00      0.00      0.00
> 
> Been running stress --cpu 8 since 18:47 and so far it is using all 8 cores at 100%. It would normally have shown the 7/8ths problem after 20s or so, maybe 2 or 3 minutes at max. So I'd say this setting is definitely involved.
> 

Thank you very much for testing. I'm not a scheduler expert, but I see 
that CONFIG_SCHED_CLUSTER is enabled by default on arm64 [0]. 

Peter is the maintainer and author of this series. 
@Peter, do you have any further insights? Thank you!

This thread background is here[1].

[0]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7bd291abe2da09f59dca81f35a4ec220e5e138a2
[1]: https://lore.kernel.org/all/f15f8166-c1e4-45dc-9ddd-4ec887e415eb@gdead.co.uk/

-- 
Best, 
Chaoyi