From nobody Mon Jan 5 11:18:47 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4D418E784AD for ; Mon, 2 Oct 2023 13:34:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237444AbjJBNeG (ORCPT ); Mon, 2 Oct 2023 09:34:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56278 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237182AbjJBNeC (ORCPT ); Mon, 2 Oct 2023 09:34:02 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3D18EAD; Mon, 2 Oct 2023 06:33:59 -0700 (PDT) Date: Mon, 02 Oct 2023 13:33:56 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1696253637; h=from:from:sender:sender:reply-to: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=Z4vR6z7FcgztoBF309slRuSBwJPiM/3Isa9tBEl+Gr0=; b=mOJ+wbg3OBccfwNWEYBZbcCYMawV5RuSyL8mWFnE1C5W6UDEsuoJRmSyxbm/E+AceRWRDp wCSDTc+zv1QLsin+RWZZ8WQ/tKfRaTiMvikuyjvGT+u+Kfhc7OQ56FPn0BcwDpRXKr9Muz ONIcZq6wdMrA1BryC7pZ17DtQPKA6H4jzhyMo/I+89cCZEywhQl4fM2f2QxN5J6/EFDMO9 fRym3PgiRlQXYF8rF1ZL6ZeC7Ks5NMhP8VE0C07vWMvtyNk3MyS5Ya2JOn4ny6n744bnLG GCBnlSKedpvvDjsuQaveqDHMUGbfvztbvsQ7M7sADrIPC2rSYA+2HCfh8GqHzw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1696253637; h=from:from:sender:sender:reply-to: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=Z4vR6z7FcgztoBF309slRuSBwJPiM/3Isa9tBEl+Gr0=; b=brH8OE/sPQOW3CTRM+SLFYrHvoA67gjNTKNsBjd4giBKIO3CwBns8VMBzg2FORkMAwJqn2 1OkfYOjoxIbLtkBg== From: "tip-bot2 for Cyril Hrubis" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched/rt/docs: Use 'real-time' instead of 'realtime' Cc: Cyril Hrubis , Ingo Molnar , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20231002115553.3007-4-chrubis@suse.cz> References: <20231002115553.3007-4-chrubis@suse.cz> MIME-Version: 1.0 Message-ID: <169625363643.3135.2547495399686514705.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: 83494dc51033506eb60c5e11a335461b2dc42111 Gitweb: https://git.kernel.org/tip/83494dc51033506eb60c5e11a335461b2= dc42111 Author: Cyril Hrubis AuthorDate: Mon, 02 Oct 2023 13:55:53 +02:00 Committer: Ingo Molnar CommitterDate: Mon, 02 Oct 2023 15:17:14 +02:00 sched/rt/docs: Use 'real-time' instead of 'realtime' Standardize on a single variant. Signed-off-by: Cyril Hrubis Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20231002115553.3007-4-chrubis@suse.cz --- Documentation/scheduler/sched-rt-group.rst | 34 ++++++++++----------- 1 file changed, 17 insertions(+), 17 deletions(-) diff --git a/Documentation/scheduler/sched-rt-group.rst b/Documentation/sch= eduler/sched-rt-group.rst index a16bee8..d685609 100644 --- a/Documentation/scheduler/sched-rt-group.rst +++ b/Documentation/scheduler/sched-rt-group.rst @@ -39,10 +39,10 @@ Most notable: 1.1 The problem --------------- =20 -Realtime scheduling is all about determinism, a group has to be able to re= ly on +Real-time scheduling is all about determinism, a group has to be able to r= ely on the amount of bandwidth (eg. CPU time) being constant. In order to schedule -multiple groups of realtime tasks, each group must be assigned a fixed por= tion -of the CPU time available. Without a minimum guarantee a realtime group c= an +multiple groups of real-time tasks, each group must be assigned a fixed po= rtion +of the CPU time available. Without a minimum guarantee a real-time group = can obviously fall short. A fuzzy upper limit is of no use since it cannot be relied upon. Which leaves us with just the single fixed portion. =20 @@ -50,14 +50,14 @@ relied upon. Which leaves us with just the single fixed= portion. ---------------- =20 CPU time is divided by means of specifying how much time can be spent runn= ing -in a given period. We allocate this "run time" for each realtime group whi= ch -the other realtime groups will not be permitted to use. +in a given period. We allocate this "run time" for each real-time group wh= ich +the other real-time groups will not be permitted to use. =20 -Any time not allocated to a realtime group will be used to run normal prio= rity +Any time not allocated to a real-time group will be used to run normal pri= ority tasks (SCHED_OTHER). Any allocated run time not used will also be picked u= p by SCHED_OTHER. =20 -Let's consider an example: a frame fixed realtime renderer must deliver 25 +Let's consider an example: a frame fixed real-time renderer must deliver 25 frames a second, which yields a period of 0.04s per frame. Now say it will= also have to play some music and respond to input, leaving it with around 80% C= PU time dedicated for the graphics. We can then give this group a run time of= 0.8 @@ -70,7 +70,7 @@ needs only about 3% CPU time to do so, it can do with a 0= .03 * 0.005s =3D of 0.00015s. =20 The remaining CPU time will be used for user input and other tasks. Because -realtime tasks have explicitly allocated the CPU time they need to perform +real-time tasks have explicitly allocated the CPU time they need to perform their tasks, buffer underruns in the graphics or audio can be eliminated. =20 NOTE: the above example is not fully implemented yet. We still @@ -90,12 +90,12 @@ The system wide settings are configured under the /proc= virtual file system: The scheduling period that is equivalent to 100% CPU bandwidth. =20 /proc/sys/kernel/sched_rt_runtime_us: - A global limit on how much time realtime scheduling may use. This is alw= ays + A global limit on how much time real-time scheduling may use. This is al= ways less or equal to the period_us, as it denotes the time allocated from the - period_us for the realtime tasks. Even without CONFIG_RT_GROUP_SCHED ena= bled, - this will limit time reserved to realtime processes. With + period_us for the real-time tasks. Even without CONFIG_RT_GROUP_SCHED en= abled, + this will limit time reserved to real-time processes. With CONFIG_RT_GROUP_SCHED=3Dy it signifies the total bandwidth available to = all - realtime groups. + real-time groups. =20 * Time is specified in us because the interface is s32. This gives an operating range from 1us to about 35 minutes. @@ -110,7 +110,7 @@ The system wide settings are configured under the /proc= virtual file system: The default values for sched_rt_period_us (1000000 or 1s) and sched_rt_runtime_us (950000 or 0.95s). This gives 0.05s to be used by SCHED_OTHER (non-RT tasks). These defaults were chosen so that a run-away -realtime tasks will not lock up the machine but leave a little time to rec= over +real-time tasks will not lock up the machine but leave a little time to re= cover it. By setting runtime to -1 you'd get the old behaviour back. =20 By default all bandwidth is assigned to the root group and new groups get = the @@ -118,10 +118,10 @@ period from /proc/sys/kernel/sched_rt_period_us and a= run time of 0. If you want to assign bandwidth to another group, reduce the root group's bandwid= th and assign some or all of the difference to another group. =20 -Realtime group scheduling means you have to assign a portion of total CPU -bandwidth to the group before it will accept realtime tasks. Therefore you= will -not be able to run realtime tasks as any user other than root until you ha= ve -done that, even if the user has the rights to run processes with realtime +Real-time group scheduling means you have to assign a portion of total CPU +bandwidth to the group before it will accept real-time tasks. Therefore yo= u will +not be able to run real-time tasks as any user other than root until you h= ave +done that, even if the user has the rights to run processes with real-time priority!