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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no 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 9A2A4C2BA19 for ; Wed, 15 Apr 2020 10:12:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 73BF720768 for ; Wed, 15 Apr 2020 10:12:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="jRHh+oFA" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2896313AbgDOKMf (ORCPT ); Wed, 15 Apr 2020 06:12:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55224 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S2896235AbgDOKL3 (ORCPT ); Wed, 15 Apr 2020 06:11:29 -0400 Received: from mail-wr1-x444.google.com (mail-wr1-x444.google.com [IPv6:2a00:1450:4864:20::444]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BB029C061A0F for ; Wed, 15 Apr 2020 03:11:28 -0700 (PDT) Received: by mail-wr1-x444.google.com with SMTP id f13so18398617wrm.13 for ; Wed, 15 Apr 2020 03:11:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=30de/AlaqjlX2SQ6sRQq6eEEGq+Ce5SXtlCKnRfiafQ=; b=jRHh+oFAJV8Tgx5k7HU8HwVLEOIdROElftVnkovMBaV0dYnaGaI26lfUn/Rltxvqw1 IrTzQFim4nimJ6tDEDZFwMfbSKq0gIawHT6Z6IvUOEYIaj7Ay81Vnz4gwWNIpTPjOtPk czVljyjYsxvuFUPAWIuDeVPGa2fIFL+SRSUw2CtkR6aGqnoBU5+Qsx1LEJgmZvJOQ70E zB/NPJpD6Ck87Rr2cygLCbpbiM/lRvmB7n5OYtiaKQt/ASJZUrdqqC8Asb6E+y/jCICV /JkQlg4fC4uF+OoaWM1Lya1oXpqG867D9dg2LD0bcXQyKXy02xyt0S8eL7whlZ3rc1Mr KvZw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=30de/AlaqjlX2SQ6sRQq6eEEGq+Ce5SXtlCKnRfiafQ=; b=iBd0azRfD63D7g4Q69uiO4yMHbaWwijr1UGpdN0JpucH6empii5+Z7f56C1Xcm2sRN 6yRpORMJOccIfbpHo38yYkmMSBAdG0OTLYWIFtb2RJ2jq1Y19Pk4C+5kdZCTI6craFdR 1/4wpg/R7spvdzyTK1fzk1LzgQSY4v2KfHjf2Lf9NG9+KOy5rp4AVNK37veBRvW95uLl qkzpVKMIa/ZbHWVz+Sz0+N/TTCdUasLmrVFKK7KNJh5DGIpunTpD2ER/odr7/4hKAaF1 hsz1DoDUreM4A0yo1H/yK4uC07y9yh+XbovAFAH8UMeLtWmdzjIxuflPYmFsYL6jvDpZ WPoA== X-Gm-Message-State: AGi0PuaG7iBEHg+ILRy3Ah2tuaqXvwT6v739mFrC1e5j69JZiHue1ok2 rOHQXT/8X4pLTRyZy/3H4vpS/g== X-Google-Smtp-Source: APiQypITjl8sl8rPg8i/DwZP4DdcaJAmWeApCTCpntNLn88ytBpJQ3R0bUll0FQH9UWGZ2HxNOUElA== X-Received: by 2002:adf:9d4a:: with SMTP id o10mr26328854wre.99.1586945487115; Wed, 15 Apr 2020 03:11:27 -0700 (PDT) Received: from google.com ([2a00:79e0:d:110:d6cc:2030:37c1:9964]) by smtp.gmail.com with ESMTPSA id x132sm17945135wmg.33.2020.04.15.03.11.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Apr 2020 03:11:26 -0700 (PDT) Date: Wed, 15 Apr 2020 11:11:22 +0100 From: Quentin Perret To: Qais Yousef Cc: Ingo Molnar , Peter Zijlstra , Jonathan Corbet , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Luis Chamberlain , Kees Cook , Iurii Zaikin , Valentin Schneider , Patrick Bellasi , Pavan Kondeti , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 1/2] sched/uclamp: Add a new sysctl to control RT default boost value Message-ID: <20200415101122.GA14447@google.com> References: <20200403123020.13897-1-qais.yousef@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200403123020.13897-1-qais.yousef@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Qais, On Friday 03 Apr 2020 at 13:30:19 (+0100), Qais Yousef wrote: > + /* > + * The new value will be applied to all RT tasks the next time they > + * wakeup, assuming the task is using the system default and not a user > + * specified value. In the latter we shall leave the value as the user > + * requested. > + */ > if (sysctl_sched_uclamp_util_min > sysctl_sched_uclamp_util_max || > sysctl_sched_uclamp_util_max > SCHED_CAPACITY_SCALE) { > result = -EINVAL; > goto undo; > } > > + if (sysctl_sched_rt_default_uclamp_util_min > SCHED_CAPACITY_SCALE) { > + result = -EINVAL; > + goto undo; > + } Hmm, checking: if (sysctl_sched_rt_default_uclamp_util_min > sysctl_sched_uclamp_util_min) would probably make sense too, but then that would make writing in sysctl_sched_uclamp_util_min cumbersome for sysadmins as they'd need to lower the rt default first. Is that the reason for checking against SCHED_CAPACITY_SCALE? That might deserve a comment or something. > @@ -1241,9 +1293,13 @@ static void uclamp_fork(struct task_struct *p) > for_each_clamp_id(clamp_id) { > unsigned int clamp_value = uclamp_none(clamp_id); > > - /* By default, RT tasks always get 100% boost */ > + /* > + * By default, RT tasks always get 100% boost, which the admins > + * are allowed to change via > + * sysctl_sched_rt_default_uclamp_util_min knob. > + */ > if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN)) > - clamp_value = uclamp_none(UCLAMP_MAX); > + clamp_value = sysctl_sched_rt_default_uclamp_util_min; > > uclamp_se_set(&p->uclamp_req[clamp_id], clamp_value, false); > } And that, as per 20200414161320.251897-1-qperret@google.com, should not be there :) Otherwise the patch pretty looks good to me! Thanks, Quentin