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

[Andrea Righi]

On Sat, Oct 17, 2026 at 10:16:00PM -1000, Tejun Heo wrote:
> 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.

Right, fair enough.

-Andrea