From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout-p-101.mailbox.org (mout-p-101.mailbox.org [80.241.56.151]) (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 2E0B547CC96; Mon, 11 May 2026 22:08:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=80.241.56.151 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778537341; cv=none; b=KHfF/osviW3I9IS+8pVXM0DFuq2WE/LMYvdvc3EirLXl5W+WqZ39QBfUz5+jdv1WMK5a/GKj806CwaNQ4w4UtbCN+JhmL52PvrveuMXlsvzBvBrOwCFEdEg/cVxt57eN/u0iky2AH+16fuLl1LOdz/E2o29D1NPDG5fR8glToss= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778537341; c=relaxed/simple; bh=AfDkvRA0WNlGZEonHbXBHom6GyQnYzGd86xVWsF0x08=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=FnTmK8Sbe6MOoiv3V9siwqAUyNxRFDdIHaelubyZdjGTP6xV92uNNVdYHFocbHTAKH2JZEcosA2Nr/LAluyiCpVOZ9Yofsf6CdejX56yr6kvK8Qan22Dq/34V9sfqV08SRMiKS2ZXxl5nSCNuj6xp/pOvvc+LRgu/6ZHElB8EQU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=mailbox.org; spf=pass smtp.mailfrom=mailbox.org; dkim=pass (2048-bit key) header.d=mailbox.org header.i=@mailbox.org header.b=RsUuzqPE; dkim=pass (2048-bit key) header.d=mailbox.org header.i=@mailbox.org header.b=bOdtI4p0; arc=none smtp.client-ip=80.241.56.151 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=mailbox.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mailbox.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=mailbox.org header.i=@mailbox.org header.b="RsUuzqPE"; dkim=pass (2048-bit key) header.d=mailbox.org header.i=@mailbox.org header.b="bOdtI4p0" Received: from smtp102.mailbox.org (smtp102.mailbox.org [10.196.197.102]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-101.mailbox.org (Postfix) with ESMTPS id 4gDv550cvNz9thy; Tue, 12 May 2026 00:08:57 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mailbox.org; s=mail20150812; t=1778537337; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=OwfMOER86C9OyxsWQbr78qu7EgXq0GUCfI5AjQ12ehQ=; b=RsUuzqPEdKlT3k/7rfSAih+BLui+KDVee0g9JzJV8XhkfEicf9QyCTVk+GGaRjcVK/VuYG qa4yie/4OjOrw8M7wzhzumzr+/PfFKPUl83SLSvyF+yQt52Ak9G4BIONkvqILG83wrr/QS vDM304dk5KQYHuOyzwkieZzEcjyefqeffVx55Caok0csBdMMJCLHU2GKeqO7uCZT3zjXMm ybUtU+XooWOcZ/73Ot7Dx1fwje95LiA5DWmmZU4YczS4i6kGCbXOy8Iq9EPqVDpz2d5SUd BWPql//uTrdr8WTYiPOkddGlU8q40/Ra15Uvho9Fv+iB5NL86XcD4ZsbZ2OJQQ== Message-ID: <4e31e3b5-fa69-4c4c-a5e9-dea7a8452ee7@mailbox.org> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mailbox.org; s=mail20150812; t=1778537335; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=OwfMOER86C9OyxsWQbr78qu7EgXq0GUCfI5AjQ12ehQ=; b=bOdtI4p0qanRqSbsCa4w1L/vLCLQI2V2bIJsC5Vn45SpOZUkP6UlR1hBwm7b6xiH7Z4LvX fgG+bkZj/d++jHtxwpyTxB9hjA7VBtnnKYA3GzmsQrYpoLyFapNlxbvbFH+ZSeYOWJZWGc tNfh3ywkcwrgbXC3EzM29DKbh7zK+nNXvlHLuZ9Ei0CPfCVqCZXTJcLZ+Ah5DU7QfNhNJI kDdkIy6zBV8pIKezCqp8BOD3/AxdLrTXZpr05/io09b1/3m754zug3R4RvJzO6o/3MCvmE QW0ZtVDqY6RmFDjVxsYJJHLYqgvV/bZrg4yeDyPtTPg0HItSlB71ezZmNj7JwQ== Date: Tue, 12 May 2026 00:08:49 +0200 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [REGRESSION] 6.12.y: d66792919d4f (sched/deadline: Use revised wakeup rule for dl_server) causes latencies up to 50ms with PREEMPT_RT To: Sasha Levin , Peter Zijlstra , Juri Lelli Cc: regressions@lists.linux.dev, stable@vger.kernel.org, linux-rt-users@vger.kernel.org, Lukas Beckmann , Mike Galbraith References: <04657838-46d1-432d-95e1-eb73b930b032@mailbox.org> <20260511141441.stable-reply-0001@kernel.org> Content-Language: en-US From: Lukas Beckmann In-Reply-To: <20260511141441.stable-reply-0001@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-MBO-RS-META: 9wk3frmm1cyqyn9ofpifscrf1adhgy88 X-MBO-RS-ID: 139742fdea8800cf756 On 5/11/26 16:21, Sasha Levin wrote: > Thanks for the detailed report. Before I revert d66792919d4f from 6.12.y, > I'd like to confirm whether the underlying issue is the missing dl_server > rework chain on 6.12.y rather than the revised wakeup rule itself. > > Mike's reply notes that his local 6.12-rt tree carrying the following > three commits in cannot reproduce, while the same tree without them > reproduces quickly: > >   cccb45d7c429 ("sched/deadline: Less agressive dl_server handling") >   4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck") >   a3a70caf7906 ("sched/deadline: Fix dl_server behaviour") > > d66792919d4f's upstream commit message explicitly says it relies on the > state established by a3a70caf7906, and none of the three are in 6.12.y. > > Could you give those three commits a spin on top of 6.12.y (keeping > d66792919d4f in place) and see whether the latency goes away? If I apply the three commits on 6.12.y, the latencies indeed go away. This is running for a few hours now, and the latencies showed up after 30 minutes tops, with plain 6.12.y before. I will leave this running. Note: I also tried applying only cccb45d7c429 ("sched/deadline: Less agressive dl_server handling") before, and that also seems to fix the issue. Thanks Lukas