Re: [PATCH v2 sched_ext/for-7.1] sched_ext: Invalidate dispatch decisions on CPU affinity changes

Cheng-Yang Chou
2026-05-05T08:35:57Z

Hi Andrea,

On Mon, May 04, 2026 at 11:58:21PM +0200, Andrea Righi wrote:
> On Mon, May 04, 2026 at 11:24:57AM -1000, Tejun Heo wrote:
> > On Mon, May 04, 2026 at 08:00:50AM +0000, Kuba Piecuch wrote:
> > > Random thought: If exposing qseq values to BPF directly is undesirable, then
> > > perhaps a less objectionable approach would be to expose them as opaque
> > > cookie/token values? Same semantics, but fewer SCX internals leaking to BPF.
> >
> > Yeah, cookie sounds fine to me and let's clearly note that this is for
> > schedulers that don't implement properly synchronized dequeue.
>
> I also like the idea of exposing cookies and extending scx_bpf_dispatch_cancel()
> to support direct dispatches, it it doesn't introduce too much complexity (it
> shouldn't be too painful).
>
> Cheng-Yang, just to make sure we're not doing the work twice, are you planning
> to work on this?

If you are already working on this, I can help with testing after your
patches! Otherwise, I'm happy to help.

FYI, I'm already working on deferring ext_server bandwidth to SCX enable
and releasing it when disabled, but it still needs more testing!

--
Cheers,
Cheng-Yang