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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 50FE3C433DF for ; Fri, 29 May 2020 15:11:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2DA5E206A4 for ; Fri, 29 May 2020 15:11:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727056AbgE2PLZ (ORCPT ); Fri, 29 May 2020 11:11:25 -0400 Received: from foss.arm.com ([217.140.110.172]:37724 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725901AbgE2PLZ (ORCPT ); Fri, 29 May 2020 11:11:25 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5D28F1045; Fri, 29 May 2020 08:11:24 -0700 (PDT) Received: from e107158-lin.cambridge.arm.com (e107158-lin.cambridge.arm.com [10.1.195.21]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A51283F718; Fri, 29 May 2020 08:11:21 -0700 (PDT) Date: Fri, 29 May 2020 16:11:18 +0100 From: Qais Yousef To: Mel Gorman Cc: Peter Zijlstra , Ingo Molnar , Randy Dunlap , Jonathan Corbet , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , 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: <20200529151118.mnysa7jv4l3ntzsk@e107158-lin.cambridge.arm.com> References: <20200511154053.7822-1-qais.yousef@arm.com> <20200528132327.GB706460@hirez.programming.kicks-ass.net> <20200528155800.yjrmx3hj72xreryh@e107158-lin.cambridge.arm.com> <20200528161112.GI2483@worktop.programming.kicks-ass.net> <20200528165130.m5unoewcncuvxynn@e107158-lin.cambridge.arm.com> <20200529102125.GB3070@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200529102125.GB3070@suse.de> User-Agent: NeoMutt/20171215 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/29/20 11:21, Mel Gorman wrote: > On Thu, May 28, 2020 at 05:51:31PM +0100, Qais Yousef wrote: > > > Indeed, that one. The fact that regular distros cannot enable this > > > feature due to performance overhead is unfortunate. It means there is a > > > lot less potential for this stuff. > > > > I had a humble try to catch the overhead but wasn't successful. The observation > > wasn't missed by us too then. > > > > As with all things, it's perfectly possible I was looking at a workload > where the cost is more obvious but given that the functions are inlined, > it's not trivial to spot. I just happened to spot it because I was paying > close attention to try_to_wake_up() at the time. Indeed. > > > On my Ubuntu 18.04 machine uclamp is enabled by default by the way. 5.3 kernel > > though, so uclamp task group stuff not there yet. Should check how their server > > distro looks like. > > > > Elsewhere in the thread, I showed some results based on 5.7 so uclamp > task group existed but I had it disabled. The uclamp related parts of > the kconfig were > > # zgrep UCLAMP kconfig-5.7.0-rc7-with-clamp.txt.gz > CONFIG_UCLAMP_TASK=y > CONFIG_UCLAMP_BUCKETS_COUNT=5 > # CONFIG_UCLAMP_TASK_GROUP is not set So you never had the TASK_GROUP part enabled when you noticed the regression? Or is it the other way around, you just disabled CONFIG_UCLAMP_TASK_GROUP to 'fix' it? Thanks -- Qais Yousef