Re: [Question] Sched: Severe scheduling latency (>10s) observed on kernel 6.12 with specific workload

[John Stultz]

On Tue, Mar 31, 2026 at 7:32 PM Xuewen Yan <xuewen.yan94@xxxxxxxxx> wrote:
>
> Dear Linux maintainers and reviewers,
>
> I am writing to report a severe scheduling latency issue we recently
> discovered on Linux Kernel 6.12.
>
> Issue Description
>
> We observed that when running a specific background workload pattern,
> certain tasks experience excessive scheduling latency. The delay from
> the runnable state to running on the CPU exceeds 10 seconds, and in
> extreme cases, it reaches up to 100 seconds.
>
> Environment Details
>
> Kernel Version: 6.12.58-android16-6-g3835fd28159d-ab000018-4k
> Architecture: [ ARM64]
> Hardware: T7300
> Config: gki_defconfig
>
> RT-app‘s workload Pattern:
>
> {
>     "tasks" : {
>             "t0" : {
>                     "instance" : 40,
>                     "priority" : 0,
>                     "cpus" : [ 0, 1, 2, 3 ],
> "taskgroup" : "/background",
>                     "loop" : -1,
>                     "run" : 200,
>                     "sleep" : 50
>             }
>     }
> }
>
> And we have applied the following patchs:
>
> https://lore.kernel.org/all/20251216111321.966709786@xxxxxxxxxxxxxxxxxxx/
> https://lore.kernel.org/all/20260106170509.413636243@xxxxxxxxxxxxxxxxxxx/
> https://lore.kernel.org/all/20260323134533.805879358@xxxxxxxxxxxxxxxxxxx/
>
>
> Could you please advise if there are known changes in the eevdf in
> 6.12 that might affect this specific workload pattern?
>

Could you maybe instead point to some source for the runqslower binary
you attached? I don't think folks will run random binaries.

Also, it looks like the RT-app description uses the background cgroup,
can you share the cgroup configuration you have set for that?

Also, did you try to reproduce this against vanilla 6.12-stable ? I'm
not sure the audience here is going to pay much attention to GKI based
reports.  Were you using any vendorhooks?

thanks
-john