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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 9EC9AC433DF for ; Thu, 28 May 2020 13:24:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 74E42207BC for ; Thu, 28 May 2020 13:24:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="oCffCv1k" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390375AbgE1NXu (ORCPT ); Thu, 28 May 2020 09:23:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60008 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390295AbgE1NXt (ORCPT ); Thu, 28 May 2020 09:23:49 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 77B27C05BD1E; Thu, 28 May 2020 06:23:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=876zKjaeAoHItKy5v6K+oJgLPOJlwJDj+y9Y+u5ub3Q=; b=oCffCv1kWlYM7vfE13NaT/An7r FivxfRrag/U7kCLFWrdaTBOn1MfgamU6vtb7+86bOlktrTuPU0RMc7tN8UBT66EdDHqq9wKLsBQwB BheUjDeh1TCkHl904kAKiyVFjkgm9qGMjitFbP0vIBf7o9YDTUSegr2VGOoABaxqQs0adNbRROgFK bvNf6ZMqbKBfKdm18q8XE4YAYrMT2/cEq2caDtfQ2VJiJ8QUZB/w6gPJSQVNqMOp1J1RjMcDYU2Kb sRZdgxRBV7TY0InZfFLKWsUxav6oCggbvU7rLVIx6d97gCuIe5HxWQtqUre10DFvb21uVR8jTDgLJ n2Vl6v4g==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jeIVQ-00056k-0N; Thu, 28 May 2020 13:23:32 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id C9832307643; Thu, 28 May 2020 15:23:27 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id BD35D20D0904E; Thu, 28 May 2020 15:23:27 +0200 (CEST) Date: Thu, 28 May 2020 15:23:27 +0200 From: Peter Zijlstra To: Qais Yousef Cc: Ingo Molnar , Randy Dunlap , Jonathan Corbet , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Luis Chamberlain , Kees Cook , Iurii Zaikin , Quentin Perret , 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: <20200528132327.GB706460@hirez.programming.kicks-ass.net> References: <20200511154053.7822-1-qais.yousef@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200511154053.7822-1-qais.yousef@arm.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, May 11, 2020 at 04:40:52PM +0100, Qais Yousef wrote: > +/* > + * By default RT tasks run at the maximum performance point/capacity of the > + * system. Uclamp enforces this by always setting UCLAMP_MIN of RT tasks to > + * SCHED_CAPACITY_SCALE. > + * > + * 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 only affects RT tasks that their uclamp_se->user_defined == false. > + * > + * This knob will not override the system default sched_util_clamp_min defined > + * above. > + * > + * Any modification is applied lazily on the next attempt to calculate the > + * effective value of the task. > + */ > +unsigned int sysctl_sched_uclamp_util_min_rt_default = SCHED_CAPACITY_SCALE; > + > /* All clamps are required to be less or equal than these values */ > static struct uclamp_se uclamp_default[UCLAMP_CNT]; > > @@ -872,6 +892,28 @@ unsigned int uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id, > return uclamp_idle_value(rq, clamp_id, clamp_value); > } > > +static inline void uclamp_sync_util_min_rt_default(struct task_struct *p, > + enum uclamp_id clamp_id) > +{ > + unsigned int default_util_min = sysctl_sched_uclamp_util_min_rt_default; > + struct uclamp_se *uc_se; > + > + /* Only sync for UCLAMP_MIN and RT tasks */ > + if (clamp_id != UCLAMP_MIN || !rt_task(p)) > + return; > + > + uc_se = &p->uclamp_req[UCLAMP_MIN]; > + > + /* > + * Only sync if user didn't override the default request and the sysctl > + * knob has changed. > + */ > + if (uc_se->user_defined || uc_se->value == default_util_min) > + return; > + > + uclamp_se_set(uc_se, default_util_min, false); > +} So afaict this is directly added to the enqueue/dequeue path, and we've recently already had complaints that uclamp is too slow. Is there really no other way?