Re: [RFC][PATCH] sched/ext: Split curr|donor references properly

[Joel Fernandes]

> On Dec 6, 2025, at 10:59 AM, Tejun Heo <tj@xxxxxxxxxx> wrote:
> 
> Hello,
> 
> On Sat, Dec 06, 2025 at 09:56:50AM -0500, Joel Fernandes wrote:
> ...
>> At a high level, my understanding is BPF schedulers have a lot of say in how to
>> schedule including precise time slice and preemption control (give or take level
>> of control and performance reasons). You can in fact have your own 'userland'
>> queues that the kernel is unaware, IIUC. I am not sure if proxy exec will
>> transparently work for all those usecases. It will probably work properly only
>> when BPF scheduling in userland is simple and most of the scheduling is done by
>> non-BPF kernel code.
> 
> Maybe this can be resolved by proxy execution explicitly telling sched_ext
> to essentially dequeue the proxy-executed task so that it's kept more
> transparent.

Yes, perhaps.

> However, I wonder whether it'd be a useful first step to first
> deconflict the two config options. ie. Allow sched_ext loading disable proxy
> execution dynamically so that people don't have to choose between the two
> config options. I don't know the code intimately, but, from just skimming
> it, it looks like it can be drained with a static key and some percpu
> counters.

Agreed. There is also stop_machine if all else fails :)

thanks,

 - Joel

> 
> Thanks.
> 
> --
> tejun