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Tue, 30 Sep 2025 00:56:20 -0700 (PDT) Date: Tue, 30 Sep 2025 15:56:02 +0800 From: Aaron Lu To: K Prateek Nayak Cc: Valentin Schneider , Ben Segall , Peter Zijlstra , Chengming Zhou , Josh Don , Ingo Molnar , Vincent Guittot , Xi Wang , linux-kernel@vger.kernel.org, Juri Lelli , Dietmar Eggemann , Steven Rostedt , Mel Gorman , Chuyi Zhou , Jan Kiszka , Florian Bezdeka , Songtang Liu , Chen Yu , Matteo Martelli , Michal =?iso-8859-1?Q?Koutn=FD?= , Sebastian Andrzej Siewior Subject: Re: [PATCH] sched/fair: Prevent cfs_rq from being unthrottled with zero runtime_remaining Message-ID: <20250930075602.GA510@bytedance> References: <20250929074645.416-1-ziqianlu@bytedance.com> <7c93d622-49fe-4e99-8142-aed69d48aa8a@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7c93d622-49fe-4e99-8142-aed69d48aa8a@amd.com> On Mon, Sep 29, 2025 at 03:04:03PM +0530, K Prateek Nayak wrote: ... ... > Can we instead do a check_enqueue_throttle() in enqueue_throttled_task() > if we find cfs_rq->throttled_limbo_list to be empty? > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 18a30ae35441..fd2d4dad9c27 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5872,6 +5872,8 @@ static bool enqueue_throttled_task(struct task_struct *p) > */ > if (throttled_hierarchy(cfs_rq) && > !task_current_donor(rq_of(cfs_rq), p)) { /* * Make sure to throttle this cfs_rq or it can be unthrottled * with no runtime_remaining and gets throttled again on its * unthrottle path. */ > + if (list_empty(&cfs_rq->throttled_limbo_list)) > + check_enqueue_throttle(cfs_rq); BTW, do you think a comment is needed? Something like the above, not sure if it's too redundant though, feel free to let me know your thoughts, thanks. > list_add(&p->throttle_node, &cfs_rq->throttled_limbo_list); > return true; > } > ---