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 41B082749E3 for ; Tue, 21 Oct 2025 14:43:37 +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=1761057819; cv=none; b=LGgNJT7pH4tOkWyX8AbtyZGE5kTgsr3c3s/Mf9S6Cd3am+CpPDc7d0qsebqt3S53Lv8g9yR+8Phq6m9+aukC2jYOY1/bBI63/Y6X8uNQ47IyWap5fkrl1s1yJ40wsdB6p7+fiyL2Kzl7SVrApnz6MiSYzVl9ZEUeuR/PH7XyyZY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761057819; c=relaxed/simple; bh=oZH73HwDHaeAO/HEhyjMk3U0j+tByEMowX5f4r4SM00=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=i8g8OptQWQALjYVxu6AXFpWUCaV9seW09zUhoW8fIJq8BULIAqQLnZ6If4X4vXf7F2Q0BzWCcSgtFdRVx/MtsJE12wCLrp8WF9aO6u3P3D6YCyufHkWaIuHrXitTGVjMTkeXl86BoJsR8k86SXkEuQy1mRfqpBzwlSFnZ557h9o= 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=UBoHV248; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=7zE+e4VT; 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="UBoHV248"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="7zE+e4VT" From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1761057816; 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=OQY4fSAjtHt0cLOVpt5VGH3RqzsBuAghRn0J25QtCNM=; b=UBoHV2488/dmjOMq/LDQEhsA6XNnLP38N2nXA4lYa5je2R8ZsjdS7yiOuM5N86J8wfwKB6 /SK++swiU72Aut7K8GNo8+MBp4IyGIpCLhP0aSNyVaTbRDVvYlrWXhCUuPmwIyxbehgUIc RVWP2gWzpql1WyXX3q/fGJsjPuPFZv0efVSez4KmhoFIfPu9BT6yBb/If61dQpcWv9XDRy oAMRc3C/1eF7X1kRHGkhgb1XIyzIMV6xhrmqu/AiWJ4lIv7VYm6aDVuMWA3d9In28+f68F jGM9kx3MNnY12QJn5rVQWVT3zszP6zboOU8hBWo4pQJ3Ue+yjVJohEkk8RWE0A== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1761057816; 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=OQY4fSAjtHt0cLOVpt5VGH3RqzsBuAghRn0J25QtCNM=; b=7zE+e4VTqu6cnGFLaD0bsKFz/oWnMxnPM/F2w9xWrAbE+n6DEgNQ8arTJxf9ZM70mcP9Dz T0ip9blTaETTzdAA== To: "KHUENY.Gerhard" Cc: "KHUENY.Gerhard" , "'linux-rt-users@vger.kernel.org'" Subject: Re: Realtime throttling and Real-Time group scheduling In-Reply-To: References: <874irt6hk8.fsf@jogness.linutronix.de> Date: Tue, 21 Oct 2025 16:49:36 +0206 Message-ID: <87frbce2nb.fsf@jogness.linutronix.de> Precedence: bulk X-Mailing-List: linux-rt-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On 2025-10-21, KHUENY.Gerhard wrote: >> > I'm running a 6.12.39-rt Linux kernel and have been experimenting with >> > runtime throttling on my embedded hardware. However, it seems that >> > the settings for sched_rt_period_us and sched_rt_runtime_us have no >> > effect. In my kernel configuration, CONFIG_RT_GROUP_SCHED is not set. >> > >> > Is my understanding correct that CONFIG_RT_GROUP_SCHED is not required >> > to throttle real-time tasks? >> >> Yes. But instead of adjusting "throttling", you adjust the guaranteed >> bandwidth for !rt tasks. You can read about the fair deadline server in its >> original commit message [0]. >> >> Basically you can adjust these debugfs files: >> >> /sys/kernel/debug/sched/fair_server/cpu*/runtime >> >> to guarantee bandwith for !rt tasks. >> >> And yes, we are aware that proper documentation for this is missing. >> >> John Ogness >> >> [0] >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/Do >> cumentation?&id=a110a81c52a9de73e2e57e826dd3bf0fd4c22226 > > Thanks for clarification. So this means that if CONFIG_RT_GROUP_SCHED > is not set, the parameters /proc/sys/kernel/sched_rt_period and > /proc/sys/kernel/sched_rt_runtime have no effect? They have no effect on the "RT throttling" feature, which does not exist for CONFIG_RT_GROUP_SCHED=n. See where it was removed here [1]. However, the parameters are still used for admission control of SCHED_DEADLINE tasks. And likewise they also affect what values can be written to /sys/kernel/debug/sched/fair_server/cpu*/runtime to configure the fair deadline server. Note that this is all new starting with v6.12. John Ogness [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5f6bd380c7bdbe10f7b4e8ddcceed60ce0714c6d