From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9431B4E4C30 for ; Thu, 1 Oct 2026 14:33:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790865218; cv=none; b=pkLMhR4rOK6+iPyJXFzLiaWoDQOnXA/GuMmZCfqdArQr9NLt0U0gdqrErb9SnSeHwzLmSr4D6fX+5Y+vT+/LUwj3VW8ZNoWqzYoyGDqcYh6CIkZ+fxWjM6uF0rjvh3v/svxbYxC4vkYii7tIAwe+3cJK+CkHZOi0MJPpqosBMXk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790865218; c=relaxed/simple; bh=LonrL9EHvB1uWkvI7vBt43f9Cw/m2q2nV8lmC9N0IKk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=UG5Dx13ZKxfXsav4ueaznp01mrki1exdmoLCT9zcLNWRS79NnGmRRkAmoWMCt5I/fWIdyjROk01M270TYVzKZhUHB4SBYs9kluvBIDPcm70QPcAgRN2vfwt7iDXXXz8l5asSAv0R/iVcsrX1n2/Uz5hrw2ZAkeLoK//t6dS/x1A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=hz3Jhibb; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="hz3Jhibb" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=M3r400i3RiYhodwFtT3hJImAZ+LcDFZg8kKGWFnvVuQ=; b=hz3JhibbIc4HsdJ23iq8HiO5Ej gv7EGENy3No8Gi97h47vQnT34crAszdNwzEO55ezx0hxtGErOfc19D6gAJqe4ZseGNVTUB+sMbb8d 0oLWfiaB33J53EdAXhCLBJR0G3aPKDJPoVcwkDAxBn1Fq33Q6etwIkyqQAQZf31YQtQ/aGReqkBE1 IYst9cy3yXIl9gn7qc/zZ9x2zpcCHSXLUsBQKYzt3ZQzcuCs/2MIvd5jJB+e1Ah5S+JcsLGb5VWyZ JB3o8YMFRrjDDZgigUNMzW9kLrV4H8fpDLAgjVDcgN2RpNxSNTCl3nEuTgkyAWXTXgghMzckvmVqp y+GkFgPA==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1xCHqU-000000083Ef-24rQ; Thu, 01 Oct 2026 14:33:15 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 17129300578; Thu, 01 Oct 2026 16:33:14 +0200 (CEST) Date: Thu, 1 Oct 2026 16:33:14 +0200 From: Peter Zijlstra To: Juri Lelli Cc: Ingo Molnar , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Andrea Righi , Frederic Weisbecker , linux-kernel@vger.kernel.org, David Haufe , Cao Ruichuang , Furkan =?utf-8?B?w4dhbMSxxZ9rYW4=?= Subject: Re: [PATCH v2] sched/deadline: Make dl-server nohz full aware Message-ID: <20261001143314.GK4121620@noisy.programming.kicks-ass.net> References: <20260513-upstream-fix-dlserver-nohzfull-b4-v2-1-d3e9cbe5c845@redhat.com> <20261001142735.GT2009045@noisy.programming.kicks-ass.net> 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: <20261001142735.GT2009045@noisy.programming.kicks-ass.net> On Thu, Oct 01, 2026 at 04:27:36PM +0200, Peter Zijlstra wrote: > > bool sched_can_stop_tick(struct rq *rq) > > { > > /* Deadline tasks, even if single, need the tick */ > > if (rq->dl.dl_nr_running) > > return false; > > > > /* > > + * If there are RT tasks, we may need the tick (for >1 RR tasks), > > + * but we must also service lower-priority CFS/SCX tasks via dl-servers. > > */ > > + if (rq->rt.rt_nr_running) { > > + bool cfs_or_scx_queued = false; > > + > > + if (rq->cfs.h_nr_queued) { > > + dl_server_start(&rq->fair_server); > > + cfs_or_scx_queued = true; > > + } > > +#ifdef CONFIG_SCHED_CLASS_EXT > > + if (rq->scx.nr_running) { > > + dl_server_start(&rq->ext_server); > > + cfs_or_scx_queued = true; > > + } > > +#endif > > + if (cfs_or_scx_queued) > > return false; What the purpose of this boolean, both true assignments above can simply be return false, no? > > > > + /* > > + * Only RT tasks, no CFS/SCX. Stop servers to prevent spurious No DL either, you've filtered those out above. > > + * wakeups. Tick can stop for single RR or any FIFO, but must > > + * run for multiple RR (round-robin behavior). > > + */ > > + dl_servers_stop_all(rq); > > + if (rq->rt.rr_nr_running > 1) > > + return false; > > return true; > > + }