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 A75CCC432C0 for ; Wed, 20 Nov 2019 19:55:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 899B82182A for ; Wed, 20 Nov 2019 19:55:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727802AbfKTTz2 (ORCPT ); Wed, 20 Nov 2019 14:55:28 -0500 Received: from foss.arm.com ([217.140.110.172]:45450 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727702AbfKTTz0 (ORCPT ); Wed, 20 Nov 2019 14:55:26 -0500 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 2BA541FB; Wed, 20 Nov 2019 11:55:26 -0800 (PST) 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 795BB3F6C4; Wed, 20 Nov 2019 11:55:24 -0800 (PST) Date: Wed, 20 Nov 2019 19:55:22 +0000 From: Qais Yousef To: Vincent Guittot Cc: linux-kernel , Ingo Molnar , Peter Zijlstra , Phil Auld , Valentin Schneider , Srikar Dronamraju , Quentin Perret , Dietmar Eggemann , Morten Rasmussen , Hillf Danton , Parth Shah , Rik van Riel Subject: Re: [PATCH v4 11/11] sched/fair: rework find_idlest_group Message-ID: <20191120195521.nvhzvd3x7l7jdxsr@e107158-lin.cambridge.arm.com> References: <1571405198-27570-12-git-send-email-vincent.guittot@linaro.org> <20191120115844.scli3gprgd5vvlt4@e107158-lin.cambridge.arm.com> <20191120173431.b7e4jbq44mjletfe@e107158-lin.cambridge.arm.com> <20191120181002.lh7vukjm2ifhysbc@e107158-lin.cambridge.arm.com> <20191120182731.z2sh5ju7uir5s3cp@e107158-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20171215 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/20/19 20:28, Vincent Guittot wrote: > I run few more tests and i can get either hw counter with 0 or not. > The main difference is on which CPU it runs: either big or little > little return always 0 and big always non-zero value > > on v5.4-rc7 and tip/sched/core, cpu0-3 return 0 and other non zeroa > but on next, it's the opposite cpu0-3 return non zero ratio > > Could you try to run the test with taskset to run it on big or little ? Nice catch! Yes indeed using taskset and forcing it to run on the big cpus it passes even on linux-next/next-20191119. So the relation to your patch is that it just biased where this test is likely to run in my case and highlighted the breakage in the counters, probably? FWIW, if I use taskset to force always big it passes. Always small, the counters are always 0 and it passes too. But if I have mixed I see what I pasted before, the counters have valid value but nhw is 0. So the questions are, why little counters aren't working. And whether we should run the test with taskset generally as it can't handle the asymmetry correctly. Let me first try to find out why the little counters aren't working. Thanks -- Qais Yousef