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Message-ID: <ZtpYGQ73WQcb95Fe@slm.duckdns.org> Date: Thu, 5 Sep 2024 15:17:13 -1000 From: Tejun Heo <tj@...nel.org> To: Peter Zijlstra <peterz@...radead.org> Cc: David Vernet <void@...ifault.com>, linux-kernel@...r.kernel.org, kernel-team@...a.com Subject: Re: [PATCH sched_ext/for-6.12] sched_ext: Handle cases where pick_task_scx() is called without preceding balance_scx() On Thu, Sep 05, 2024 at 06:41:42AM -1000, Tejun Heo wrote: > > @@ -12716,6 +12716,12 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf) > > if (this_rq->cfs.h_nr_running && !pulled_task) > > pulled_task = 1; > > > > + /* > > + * We pulled a task, but it got stolen before we re-acquired rq->lock. > > + */ > > + if (!this_rq->cfs.h_nr_running && pulled_task) > > + pulled_task = 0; > > + > > Lemme test that. Did a bit of testing and it seems like it's mostly coming from delayed dequeue handling. pick_next_entity() does this: struct sched_entity *se = pick_eevdf(cfs_rq); if (se->sched_delayed) { dequeue_entities(rq, se, DEQUEUE_SLEEP | DEQUEUE_DELAYED); SCHED_WARN_ON(se->sched_delayed); SCHED_WARN_ON(se->on_rq); return NULL; } rq->cfs.nr_running includes the number of delay dequeued tasks which aren't really runnable, so it seems like balance_fair() saying yes and pick_next_entity() then hitting a delayed task. Maybe the solution is tracking the number of delayed ones and subtracting that from nr_running? I'm trying that but can't get the delayed count straight for some reason. Thanks. -- tejun
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