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=-14.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 91FFBC433E0 for ; Wed, 29 Jul 2020 12:02:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 725B320829 for ; Wed, 29 Jul 2020 12:02:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="YluZYPuB"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="rZZD2Qsp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727054AbgG2MCi (ORCPT ); Wed, 29 Jul 2020 08:02:38 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:41640 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726341AbgG2MCh (ORCPT ); Wed, 29 Jul 2020 08:02:37 -0400 Date: Wed, 29 Jul 2020 12:02:33 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1596024155; 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=Q3fiI8kEzJLzx7f9GhNpHCCPryXYwTat7MLMxiPCCdQ=; b=YluZYPuBL31TPlM0SFM0AHBTwI26HjSDAmmNHIYtQNnT6vcNPKte5Z5imDu2Cfmt8HADgv UA6aTWa57FI/nYznXnJzKs3dfFLemigoA+DZLgqZ1Faf9VNc2Rd9phYaoRB3IS5jHl8t0p Fj9kobpHoNuGdB0qF0ru2Ws7qrJmKT4/XR7sj+HVShJbJSQbhML5sJJGtXus9vdEiEIR7B HvCDUQjWXZUnV8ghXIRp4LYdJPYW/Ka4Zm5+PuoBgbnPBTAd7YALdb+AbYK0J4BSF3ibph OBDlUw22QpGjFE8pZ5RE8yjXElfzpeZOnNyKMJvLd9ptMCmHuGDlLkVbr/gQ0A== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1596024155; 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=Q3fiI8kEzJLzx7f9GhNpHCCPryXYwTat7MLMxiPCCdQ=; b=rZZD2QspO6hG6D6caBRD0nPhqXYiRySg5zkxthbgi70Hj3ujyKOZgeJPoBATfwMtV+IdCJ OZO4p7hAlURAU3BA== From: "tip-bot2 for Qais Yousef" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] Documentation/sysctl: Document uclamp sysctl knobs Cc: Qais Yousef , "Peter Zijlstra (Intel)" , x86 , LKML In-Reply-To: <20200716110347.19553-3-qais.yousef@arm.com> References: <20200716110347.19553-3-qais.yousef@arm.com> MIME-Version: 1.0 Message-ID: <159602415378.4006.11058141925168356516.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: 7bit Sender: linux-kernel-owner@vger.kernel.org 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: 1f73d1abe5836bd8ffe747ff5cb7561b17ce5bc6 Gitweb: https://git.kernel.org/tip/1f73d1abe5836bd8ffe747ff5cb7561b17ce5bc6 Author: Qais Yousef AuthorDate: Thu, 16 Jul 2020 12:03:46 +01:00 Committer: Peter Zijlstra CommitterDate: Wed, 29 Jul 2020 13:51:48 +02:00 Documentation/sysctl: Document uclamp sysctl knobs Uclamp exposes 3 sysctl knobs: * sched_util_clamp_min * sched_util_clamp_max * sched_util_clamp_min_rt_default Document them in sysctl/kernel.rst. Signed-off-by: Qais Yousef Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200716110347.19553-3-qais.yousef@arm.com --- Documentation/admin-guide/sysctl/kernel.rst | 54 ++++++++++++++++++++- 1 file changed, 54 insertions(+) diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index 83acf50..55bf6b4 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -1062,6 +1062,60 @@ Enables/disables scheduler statistics. Enabling this feature incurs a small amount of overhead in the scheduler but is useful for debugging and performance tuning. +sched_util_clamp_min: +===================== + +Max allowed *minimum* utilization. + +Default value is 1024, which is the maximum possible value. + +It means that any requested uclamp.min value cannot be greater than +sched_util_clamp_min, i.e., it is restricted to the range +[0:sched_util_clamp_min]. + +sched_util_clamp_max: +===================== + +Max allowed *maximum* utilization. + +Default value is 1024, which is the maximum possible value. + +It means that any requested uclamp.max value cannot be greater than +sched_util_clamp_max, i.e., it is restricted to the range +[0:sched_util_clamp_max]. + +sched_util_clamp_min_rt_default: +================================ + +By default Linux is tuned for performance. Which means that RT tasks always run +at the highest frequency and most capable (highest capacity) CPU (in +heterogeneous systems). + +Uclamp achieves this by setting the requested uclamp.min of all RT tasks to +1024 by default, which effectively boosts the tasks to run at the highest +frequency and biases them to run on the biggest CPU. + +This knob allows admins to change the default behavior when uclamp is being +used. In battery powered devices particularly, running at the maximum +capacity and frequency will increase energy consumption and shorten the battery +life. + +This knob is only effective for RT tasks which the user hasn't modified their +requested uclamp.min value via sched_setattr() syscall. + +This knob will not escape the range constraint imposed by sched_util_clamp_min +defined above. + +For example if + + sched_util_clamp_min_rt_default = 800 + sched_util_clamp_min = 600 + +Then the boost will be clamped to 600 because 800 is outside of the permissible +range of [0:600]. This could happen for instance if a powersave mode will +restrict all boosts temporarily by modifying sched_util_clamp_min. As soon as +this restriction is lifted, the requested sched_util_clamp_min_rt_default +will take effect. seccomp =======