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 01BAA36E48C for ; Thu, 30 Jul 2026 10:05:08 +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=1785405911; cv=none; b=ICle7UtTvjSDa25qC/YqDuCQmJPPVrrVK29p41n/u7hdLNJGh2YgkgF35kXtP9ZubdBXqQrxC+04ffbRh/0M4GrE6krJF4Ui3aK3Kv87U+SwDgp+z39eKe2DZ0ZnmmVcSghzOY5C7PWdKiq5WgoHJPjS23TmQXLQZTykSnp+NIQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785405911; c=relaxed/simple; bh=JLETZVW+sCQhL21jH4nTrOsfhKrxmIm2D8kMALIs/X0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ADKKmYVVHrPl5FGVG+k2U2DNeWi2NNRUJjEQNmW/jfeZQ6CKWcYd8o3OlpBxglH8oBvMYXVFigr/99ffyWAMCpHRe7iR65SzY1Jp/CECmjvZDWl2Yqdep4Qy39hDdiYV7FRcY+OpjZfgBb7S0nx7Oo6E9JkFrwsfeTMlygj9gyg= 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=tIVGcykU; 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="tIVGcykU" 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=Vn2VOFOaCcMfDMmpoMTkUUbPSIzxNExSRRXH03YMQ9o=; b=tIVGcykU+blm8VbHEwCFbFnUqi xwjcyyo5Kbh20rkJF/I5VRD3IUSnmw3K0dOhNm3HaHyo3lJxhE+WNQfTqNx9LiSHYnEnfbib1sDqq 9920bAZzoaskVB636UktoAaP72X9zD5ub16w7fRPhdfcInLuYnqLdj9iQlJQdyZwPvqmBTfZgoiE4 WRt7/PFXYRm9GsST9qAkyBcNjylRa0dI/+IdMMJTQP4Egs8/zOyyTPixMXLwl8D65v0F2SKmVmCBR /5qub6eEZ1zmaCrCm+yPj8uITKNxoNwWoNpwH+krEDL5I0AmfZPitE5zE1C1jDVd767pDuo3wfxlQ 54YbMT0A==; 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 1wpNdK-0000000At2j-1SKy; Thu, 30 Jul 2026 10:04:58 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 5749930095A; Thu, 30 Jul 2026 12:04:57 +0200 (CEST) Date: Thu, 30 Jul 2026 12:04:57 +0200 From: Peter Zijlstra To: Andrea Righi Cc: Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Tejun Heo , Patrick Bellasi , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] sched/deadline: Skip bandwidth accounting with SCHED_FLAG_KEEP_PARAMS Message-ID: <20260730100457.GP49951@noisy.programming.kicks-ass.net> References: <20260730055011.2267333-1-arighi@nvidia.com> <20260730055631.2271580-1-arighi@nvidia.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: <20260730055631.2271580-1-arighi@nvidia.com> On Thu, Jul 30, 2026 at 07:56:31AM +0200, Andrea Righi wrote: > A sched_setattr() invocation targeting a non-deadline task can specify > SCHED_DEADLINE together with SCHED_FLAG_KEEP_PARAMS. The flag prevents > __sched_setscheduler() from applying the requested parameters or class, > but deadline admission runs before the guarded update and immediately > accounts the requested bandwidth in the root domain. Repeating the > invocation can therefore consume bandwidth without creating a deadline > task capable of releasing it. > > Skip deadline bandwidth admission when SCHED_FLAG_KEEP_PARAMS is set, > since neither the deadline policy nor its parameters will change. I'm thinking this should be fixed by simply not allowing KEEP_PARAM when the policy changes, no?