From nobody Wed Jan 7 04:02:31 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 383AEE784A4 for ; Mon, 2 Oct 2023 11:55:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236824AbjJBLzW (ORCPT ); Mon, 2 Oct 2023 07:55:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35380 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236812AbjJBLzU (ORCPT ); Mon, 2 Oct 2023 07:55:20 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4AB2FDD; Mon, 2 Oct 2023 04:55:17 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id B2D1F2185E; Mon, 2 Oct 2023 11:55:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1696247715; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=JsXx++ft+4VCJrpVJaIU2XEeGtrebfs0OM99VTK3rfw=; b=1Mag04Uu8qGqH6FxLtUYVFIpkO3sXmjqFUIVACEoFDjjDCL2KNJ4I9ume9PPD8RG7TTwE/ N43sWOm7p/wspFvAlrzquk2aQ8edSS+78bbIRCROKVW6C96zQT+Zcmr9/087DISvosGgcn xgIZqOY1yGjJ6Qchjr5zhKJ0Z4cM7Dg= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1696247715; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=JsXx++ft+4VCJrpVJaIU2XEeGtrebfs0OM99VTK3rfw=; b=xy1XsqQVhp51b6Y77aSP9q6sJLgyBlyAYmkIOowJElDC6zf/JLbxTR+j5P3ssRorUP4xBE XLtR/Zm1G5ynqpCA== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 9B36813434; Mon, 2 Oct 2023 11:55:15 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id gaVlJKOvGmU/FAAAMHmgww (envelope-from ); Mon, 02 Oct 2023 11:55:15 +0000 From: Cyril Hrubis To: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , linux-kernel@vger.kernel.org, Jonathan Corbet , linux-doc@vger.kernel.org Cc: ltp@lists.linux.it, Cyril Hrubis Subject: [PATCH v3 2/3] docs: scheduler-rt: Clarify & fix sched_rt_* sysctl docs Date: Mon, 2 Oct 2023 13:55:52 +0200 Message-ID: <20231002115553.3007-3-chrubis@suse.cz> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20231002115553.3007-1-chrubis@suse.cz> References: <20231002115553.3007-1-chrubis@suse.cz> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" - Describe explicitly that sched_rt_runtime_us is allocated from sched_rt_period_us and hence always less or equal to that value. - The limit for sched_rt_runtime_us is not INT_MAX-1, but rather it's limited by the value of sched_rt_period_us. If sched_rt_period_us is INT_MAX then sched_rt_runtime_us can be set to INT_MAX as well. Signed-off-by: Cyril Hrubis --- Documentation/scheduler/sched-rt-group.rst | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/Documentation/scheduler/sched-rt-group.rst b/Documentation/sch= eduler/sched-rt-group.rst index 655a096ec8fb..a16bee8f74c2 100644 --- a/Documentation/scheduler/sched-rt-group.rst +++ b/Documentation/scheduler/sched-rt-group.rst @@ -87,18 +87,20 @@ lack an EDF scheduler to make non-uniform periods usabl= e. The system wide settings are configured under the /proc virtual file syste= m: =20 /proc/sys/kernel/sched_rt_period_us: - The scheduling period that is equivalent to 100% CPU bandwidth + 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. Even witho= ut - CONFIG_RT_GROUP_SCHED enabled, this will limit time reserved to realtime - processes. With CONFIG_RT_GROUP_SCHED it signifies the total bandwidth - available to all realtime groups. + A global limit on how much time realtime scheduling may use. This is alw= ays + 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 + CONFIG_RT_GROUP_SCHED=3Dy it signifies the total bandwidth available to = all + realtime groups. =20 * Time is specified in us because the interface is s32. This gives an operating range from 1us to about 35 minutes. * sched_rt_period_us takes values from 1 to INT_MAX. - * sched_rt_runtime_us takes values from -1 to (INT_MAX - 1). + * sched_rt_runtime_us takes values from -1 to sched_rt_period_us. * A run time of -1 specifies runtime =3D=3D period, ie. no limit. =20 =20 --=20 2.41.0