From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0B241C433FE for ; Tue, 14 Sep 2021 20:34:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DF3D66115B for ; Tue, 14 Sep 2021 20:34:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233904AbhINUfh (ORCPT ); Tue, 14 Sep 2021 16:35:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40374 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232341AbhINUfg (ORCPT ); Tue, 14 Sep 2021 16:35:36 -0400 Received: from mail.skyhub.de (mail.skyhub.de [IPv6:2a01:4f8:190:11c2::b:1457]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 90A54C061574; Tue, 14 Sep 2021 13:34:18 -0700 (PDT) Received: from zn.tnic (p200300ec2f104800104a7ca086fcfa54.dip0.t-ipconnect.de [IPv6:2003:ec:2f10:4800:104a:7ca0:86fc:fa54]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id D40BA1EC0298; Tue, 14 Sep 2021 22:34:16 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1631651657; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type: content-transfer-encoding:content-transfer-encoding:in-reply-to: references; bh=ho0dIkyXb9rhQ4ltF8xF/Fh/kKjZFTuUyHYcmevz7B4=; b=mFAnc9V6M98Xy3oMHBpkH8puEf9GQ4HT6tCOMvcz22KIL9BnyevbDohEJ8tTUH/g+OODfq O5n3/1zLTzv7YcAnB3qfsu3R3UndsBwSi//8U3d2kzNDuiLtaIU6Ie853ibz75ZxPnPblM zft0USk3XtqZ/+D7z+UBI6J0V6jmh1k= From: Borislav Petkov To: Jonathan Corbet Cc: "Paul E. McKenney" , Thomas Gleixner , linux-doc@vger.kernel.org, LKML Subject: [PATCH] Documentation/no_hz: Introduce "dyntick-idle mode" before using it Date: Tue, 14 Sep 2021 22:33:55 +0200 Message-Id: <20210914203355.21360-1-bp@alien8.de> X-Mailer: git-send-email 2.29.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Borislav Petkov The CONFIG_NO_HZ_IDLE paragraph is using "dyntick-idle mode" before having defined it while the definition comes a couple of paragraphs later. That is leaving the reader with scratching head what that dyntick-idle mode might be. Pull its definition up so that it is clear. Signed-off-by: Borislav Petkov --- Documentation/timers/no_hz.rst | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/Documentation/timers/no_hz.rst b/Documentation/timers/no_hz.rst index 6cadad7c3aad..20ad23a6c618 100644 --- a/Documentation/timers/no_hz.rst +++ b/Documentation/timers/no_hz.rst @@ -70,6 +70,10 @@ interrupt. After all, the primary purpose of a scheduling-clock interrupt is to force a busy CPU to shift its attention among multiple duties, and an idle CPU has no duties to shift its attention among. +An idle CPU that is not receiving scheduling-clock interrupts is said to +be "dyntick-idle", "in dyntick-idle mode", "in nohz mode", or "running +tickless". The remainder of this document will use "dyntick-idle mode". + The CONFIG_NO_HZ_IDLE=y Kconfig option causes the kernel to avoid sending scheduling-clock interrupts to idle CPUs, which is critically important both to battery-powered devices and to highly virtualized mainframes. @@ -91,10 +95,6 @@ Therefore, systems with aggressive real-time response constraints often run CONFIG_HZ_PERIODIC=y kernels (or CONFIG_NO_HZ=n for older kernels) in order to avoid degrading from-idle transition latencies. -An idle CPU that is not receiving scheduling-clock interrupts is said to -be "dyntick-idle", "in dyntick-idle mode", "in nohz mode", or "running -tickless". The remainder of this document will use "dyntick-idle mode". - There is also a boot parameter "nohz=" that can be used to disable dyntick-idle mode in CONFIG_NO_HZ_IDLE=y kernels by specifying "nohz=off". By default, CONFIG_NO_HZ_IDLE=y kernels boot with "nohz=on", enabling -- 2.29.2