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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 954E4C43219 for ; Fri, 26 Apr 2019 04:41:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6CE3A206A3 for ; Fri, 26 Apr 2019 04:41:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="TuXUDwrV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726771AbfDZEkt (ORCPT ); Fri, 26 Apr 2019 00:40:49 -0400 Received: from mail-pl1-f194.google.com ([209.85.214.194]:38371 "EHLO mail-pl1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726303AbfDZEks (ORCPT ); Fri, 26 Apr 2019 00:40:48 -0400 Received: by mail-pl1-f194.google.com with SMTP id f36so903222plb.5 for ; Thu, 25 Apr 2019 21:40:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:subject:to:cc:references:in-reply-to:mime-version :user-agent:message-id:content-transfer-encoding; bh=HyNPJz1X169VLMtNR26KKjpc2sEs9qFQ9M2v5D+bVv8=; b=TuXUDwrVEIx8NtXEzDxtanN52U2D+wK2SVUg2swQN+sNP1mAy1NWpky8Qp5ichbZXZ GCdmxf246D//n6ZjuGOKr71xuob2KfVnGBopnrj1lvKU6n4fT2xov6t3CfV/OEpiHrc7 qE8mKU80EeFyoT0pSSgVB2gf+r81CX/9quQafpsdimBj+5KWMZD3pzSCL3yd8xxdLCkj 6HdNHuGhW7xMa6LiRX98KGp8FI5v43XY/1PIfpukn5HuyBZwg+lgx2vBCx82gp/QdKu4 ujwAT+f8aUl11vYYaVPycP9+TDbSqtbOqrIwvZWUCU7bZu0PBw8OfQEIfmmyqYr9ncg8 xWrw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:subject:to:cc:references:in-reply-to :mime-version:user-agent:message-id:content-transfer-encoding; bh=HyNPJz1X169VLMtNR26KKjpc2sEs9qFQ9M2v5D+bVv8=; b=pjAM114+7USnZAx7Sm3tYiliQWFqlEiHNUTg6kVZ+XneRhfIW1h/fATE7/r0cyaq2T z+YPtolWMG1UZha5COZax0Lt3nPZye1q7t4WY+X6OijNE5PmWkMJdTx7N3bKyHmXgRFh 8l4aPrdcbCrDYhHmojYTerVID2j3IxK5RciFpeT6u0nIGqmR+zSDNK/4qOZ2D0hBO4ME T4DDxqBqSpN0+fLsM0GOTTBjimGgh6bB4dITC942jB5DCJvTRRb1umw0T+Rhv2k7e9DG 0WS8TmzwbwuZcDHpM5xCrbYSnprnRb1HRWI0CPLHARW9Wf/FWuxOw+Ch6Mwv+cZWwVUM yScg== X-Gm-Message-State: APjAAAVAi8eqvSZfzoDVOjt+N8SrbM9uaDoNr6qqcrd4k5PXqx6hslGR KV+WfY9qJO/fMjTiClHC1Wc= X-Google-Smtp-Source: APXvYqyd4vzJ9MypgChZoEQuJwJaKshCPYVtE2Jmcv9yHyorZNU4m+/ryO0jlMGkVsV1OL3eZ3xygQ== X-Received: by 2002:a17:902:8483:: with SMTP id c3mr42057501plo.19.1556253648136; Thu, 25 Apr 2019 21:40:48 -0700 (PDT) Received: from localhost ([203.63.161.26]) by smtp.gmail.com with ESMTPSA id f22sm33926308pgv.45.2019.04.25.21.40.45 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 25 Apr 2019 21:40:46 -0700 (PDT) Date: Fri, 26 Apr 2019 14:40:40 +1000 From: Nicholas Piggin Subject: Re: [PATCH] kernel/sched: run nohz idle load balancer on HK_FLAG_MISC CPUs To: Peter Zijlstra Cc: Frederic Weisbecker , linux-kernel@vger.kernel.org, Ingo Molnar , Thomas Gleixner References: <20190412042613.28930-1-npiggin@gmail.com> <20190425115620.GQ4038@hirez.programming.kicks-ass.net> In-Reply-To: <20190425115620.GQ4038@hirez.programming.kicks-ass.net> MIME-Version: 1.0 User-Agent: astroid/0.14.0 (https://github.com/astroidmail/astroid) Message-Id: <1556253219.geomfr4bo2.astroid@bobo.none> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra's on April 25, 2019 9:56 pm: > On Fri, Apr 12, 2019 at 02:26:13PM +1000, Nicholas Piggin wrote: >> The nohz idle balancer runs on the lowest idle CPU. This can >> interfere with isolated CPUs, so confine it to HK_FLAG_MISC >> housekeeping CPUs. >>=20 >> HK_FLAG_SCHED is not used for this because it is not set anywhere >> at the moment. This could be folded into HK_FLAG_SCHED once that >> option is fixed. >=20 > Frederic? Anyway, I thnk I'll take this patch as is. That would be great, thanks. We've been testing it in a staging environment (this is where they noticed the noise in the first place), and results have been as expected: I've been able to test Nick's idle-loop load balancer (ILB) patch,=20 with and without the TEO cpuidle governor. With the ILB patch (and=20 nohz_full) I get a very quiet noise profile with either cpuidle=20 governor (menu or teo). For my tests, I don't see a meaningful=20 difference between the two governors. [...] Bottom line: Nick's patch that constrains the ILB to run on non-nohz=20 cores has a noticeable noise-reduction effect. For this type of=20 workload, the choice of cpuidle governor, menu or teo, is immaterial. This is against a slightly backported RHEL kernel they are using, but no significant differences from upstream in these areas. Thanks, Nick =