Re: [PATCH 5/6] sched_ext: Report the ecaps loss when a cpu goes offline

[Tejun Heo]

Hello, Andrea.

On Sun, Oct 18, 2026 at 09:01:18AM +0200, Andrea Righi wrote:
> With a root-only scheduler the walk skips the root and queues nothing, but
> resched_sync_ecaps() still runs on every online CPU, starting the ext_server and
> queueing the resched irq work for no reason. Can we do it only if something was
> actually queued?
...
> ame on the offline side: with no sub-sched nr is 0, but we still do
> update_rq_clock(), dl_server_start(&rq->ext_server) and the irq work on a CPU
> that's going down and the ext_server stays enqueued there until
> sched_cpu_dying() stops it. How about:

These are on the cpu hotplug path, which is really cold, and the cost is a
resched on one cpu. It's minuscule and doesn't matter, so I don't think it
makes sense to add any complexity to avoid it.

Thanks.

--
tejun