From: Andrea Righi <arighi@nvidia.com>
To: Tejun Heo <tj@kernel.org>
Cc: sched-ext@lists.linux.dev, David Vernet <void@manifault.com>,
Changwoo Min <changwoo@igalia.com>,
Emil Tsalapatis <emil@etsalapatis.com>,
David Dai <david.dai@linux.dev>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/6] sched_ext: Report the ecaps loss when a cpu goes offline
Date: Sun, 18 Oct 2026 11:18:28 +0200 [thread overview]
Message-ID: <atSO5LIzqgOYxR45@gpd4> (raw)
In-Reply-To: <b291e2b97ceef620c6330b13978da668@kernel.org>
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
next prev parent reply other threads:[~2026-10-18 9:18 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-18 1:59 [PATCHSET v3 sched_ext/for-7.4] sched_ext: Report a sub-scheduler's ecaps on attach, detach and cpu hotplug Tejun Heo
2026-10-18 1:59 ` [PATCH 1/6] sched_ext: Factor out cid_pshard() Tejun Heo
2026-10-18 1:59 ` [PATCH 2/6] sched_ext: Free a sub-scheduler a grace period after discarding its ecaps syncs Tejun Heo
2026-10-18 6:56 ` Andrea Righi
2026-10-18 8:16 ` Tejun Heo
2026-10-18 9:17 ` Andrea Righi
2026-10-18 1:59 ` [PATCH 3/6] sched_ext: Report a sub-scheduler's ecaps on attach and detach Tejun Heo
2026-10-18 1:59 ` [PATCH 4/6] sched_ext: Deliver ecaps only while the root has the cpu online Tejun Heo
2026-10-18 1:59 ` [PATCH 5/6] sched_ext: Report the ecaps loss when a cpu goes offline Tejun Heo
2026-10-18 6:49 ` Andrea Righi
2026-10-18 8:15 ` Tejun Heo
2026-10-18 7:01 ` Andrea Righi
2026-10-18 8:16 ` Tejun Heo
2026-10-18 9:18 ` Andrea Righi [this message]
2026-10-18 8:22 ` [PATCH v3 " Tejun Heo
2026-10-18 1:59 ` [PATCH 6/6] sched_ext: Leave suspend and hibernation out of the ecaps reports Tejun Heo
2026-10-18 9:19 ` [PATCHSET v3 sched_ext/for-7.4] sched_ext: Report a sub-scheduler's ecaps on attach, detach and cpu hotplug Andrea Righi
-- strict thread matches above, loose matches on Subject: below --
2026-10-17 16:45 [PATCHSET v2 " Tejun Heo
2026-10-17 16:45 ` [PATCH 5/6] sched_ext: Report the ecaps loss when a cpu goes offline Tejun Heo
2026-10-17 18:14 ` sashiko-bot
2026-10-17 18:43 ` Tejun Heo
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