linux-kernel - Re: [RFC][PATCH] sched/deadline: Fix dl_server getting stuck, allowing cpu starvation

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Message-ID: <20250916213036.GC2800598@noisy.programming.kicks-ass.net>
Date: Tue, 16 Sep 2025 23:30:36 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: John Stultz <jstultz@...gle.com>
Cc: Juri Lelli <juri.lelli@...hat.com>, LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Valentin Schneider <vschneid@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Xuewen Yan <xuewen.yan94@...il.com>,
	K Prateek Nayak <kprateek.nayak@....com>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Qais Yousef <qyousef@...alina.io>,
	Joel Fernandes <joelagnelf@...dia.com>,
	kuyo chang <kuyo.chang@...iatek.com>, hupu <hupu.gm@...il.com>,
	kernel-team@...roid.com
Subject: Re: [RFC][PATCH] sched/deadline: Fix dl_server getting stuck,
 allowing cpu starvation

On Tue, Sep 16, 2025 at 10:35:46AM -0700, John Stultz wrote:
> I of course still see the thread spawning issues with my
> ksched_football test that come from keeping the dl_server running for
> the whole period, but that's a separate thing I'm trying to isolate.

So what happens with that football thing -- you're saying thread
spawning issues, so kthread_create() is not making progress?

You're also saying 'keeping the dl_server running for the whole period',
are you seeing it not being limited to its allocated bandwidth?

Per the bug today, the dl_server does get throttled, not sufficiently?