From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 4D78946A610; Tue, 21 Jul 2026 15:52:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784649125; cv=none; b=HLSZGoBJ5pxnsscpw8M3135FmmkXZ2XHcQwZVGn+47T+ciXAFLT4al+s0RRIivyFvnSpYaeIBVmfmQST4aLZWYAiucBxwZ04t8YPojm7w3JXDgtKor2Hk00HY9yb/WcxeOMCcmhEnuVFsVUC+g+gWIPz+U/8VukJwAVNtXVfjl8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784649125; c=relaxed/simple; bh=BOJNFKFHPMWMqW4Cyo7goHnFS8Qn+Tk2Jz5ToPhtb04=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=f6UWT1yuGTlPOEiHhop/JvjfCc7qk/hU8tqjIqDKj1Uyu6r4CyuWi/HB8ba+8zOY39msIe8+32qdyqJJQeB22f/USKWVYKTbNnwTuHrAz1XBytbIr1GjfGgBS1aL/1t9j8cVkUDHX5r5z1cQhTU10PlPNp1Mz731L7h5B37j0RY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=dOrr7k/g; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=lKHiXfPP; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="dOrr7k/g"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="lKHiXfPP" From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1784649120; 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: in-reply-to:in-reply-to:references:references; bh=U7xMNVgyGGRyIJjpXA89R9vggcnCwn9+jkC/W3//MNU=; b=dOrr7k/gCpLEdMnv5dh35arkpybcWD8kCUht22t5gObuAZatCP4xhAVQjic61E2sFQzQ2S MqnoA75VFM1bMW+XlwG3nlOEbc2hUVjI8SHCBzMyHvrPYmwmSnEhgsqzB1Xeb5fbIRk8ag wKQH4iMhw6tZZmHxW64h3uQlPOB+m/uYM70sxuTXYZc3DjO0/Y6auycLAy0ENtYgtqcmkf IVML1bKkoEiVsQtZMBaZzWruMTy2HjS0cnRHK8BljUXFtAh7z1rcLe9zIXCm6D1U5h7Yoy jPh3D8HQsgywlzOaX/g5SvLVD/Bz/K4JICySxHnha5gTpj4A92mVqnWgBYgyow== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1784649120; 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: in-reply-to:in-reply-to:references:references; bh=U7xMNVgyGGRyIJjpXA89R9vggcnCwn9+jkC/W3//MNU=; b=lKHiXfPPd51EAGFq8GJ65zypWRA5lifGz5wyKa132AFkAABV3p1zQWIB7r9k7FImJRLy4W uOpCMsOhbXf0K0DQ== To: Sebastian Andrzej Siewior , Steven Rostedt Cc: "Ahmed S. Darwish" , Jonathan Corbet , Clark Williams , linux-rt-devel@lists.linux.dev, Matthew Wilcox , Derek Barbosa , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 1/1] Documentation: real-time: Add kernel configuration guide In-Reply-To: <20260721152114.wTED4bR5@linutronix.de> References: <20260716195716.256025-1-darwi@linutronix.de> <20260716195716.256025-2-darwi@linutronix.de> <20260721130248.ndwsFtHE@linutronix.de> <874ihs5s4d.fsf@jogness.linutronix.de> <20260721143606.NqT15H0p@linutronix.de> <20260721104806.64afcd8f@gandalf.local.home> <20260721152114.wTED4bR5@linutronix.de> Date: Tue, 21 Jul 2026 17:58:00 +0206 Message-ID: <87wluo49y7.fsf@jogness.linutronix.de> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On 2026-07-21, Sebastian Andrzej Siewior wrote: > On 2026-07-21 10:48:06 [-0400], Steven Rostedt wrote: >> On Tue, 21 Jul 2026 16:36:06 +0200 >> Sebastian Andrzej Siewior wrote: >> >>>> Unfortunately, debugfs is needed to configure the fair deadline server: >>>> >>>> /sys/kernel/debug/sched/fair_server/cpu*/runtime >>> >>> So drop the reference to it. It is not "bad" to have it enabled. It is >> >> I believe that some distros feel that it is bad to enable because there's >> no real auditing of its interface. Although, it is now only accessible by >> root. > > Yeah. Either way, there shouldn't be anything real-time specific that > requires the user have it enabled or disabled. The fair deadline server is certainly real-time specific. It is the new/additional RT throttling mechanism. Generally speaking, RT systems will want to disable it or at least reduce the 50ms default. This document is not about runtime settings, but if debugfs is not enabled, the user will have no way to configure the fair deadline server at runtime. I am OK if it is completely dropped from this document. But if there are distros that think it is bad, it might be worth mentioning that this config is important (if not critical) for real-time systems. John