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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 950C6C46471 for ; Mon, 6 Aug 2018 10:53:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5617821A01 for ; Mon, 6 Aug 2018 10:53:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5617821A01 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730384AbeHFNCY (ORCPT ); Mon, 6 Aug 2018 09:02:24 -0400 Received: from foss.arm.com ([217.140.101.70]:36262 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727595AbeHFNCX (ORCPT ); Mon, 6 Aug 2018 09:02:23 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BAD9818A; Mon, 6 Aug 2018 03:53:53 -0700 (PDT) Received: from [10.4.12.39] (e113632-lin.emea.arm.com [10.4.12.39]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 806763F5D4; Mon, 6 Aug 2018 03:53:52 -0700 (PDT) Subject: Re: [PATCHv4 12/12] sched/core: Disable SD_PREFER_SIBLING on asymmetric cpu capacity domains To: Vincent Guittot Cc: Morten Rasmussen , Peter Zijlstra , Ingo Molnar , Dietmar Eggemann , gaku.inami.xh@renesas.com, linux-kernel References: <1530699470-29808-1-git-send-email-morten.rasmussen@arm.com> <1530699470-29808-13-git-send-email-morten.rasmussen@arm.com> <20180706143139.GE8596@e105550-lin.cambridge.arm.com> From: Valentin Schneider Message-ID: Date: Mon, 6 Aug 2018 11:53:50 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 06/08/18 11:20, Vincent Guittot wrote: > Hi Valentin, > > On Tue, 31 Jul 2018 at 14:33, Valentin Schneider > wrote: >> >> Hi, >> >> On 31/07/18 13:17, Vincent Guittot wrote: >> [...] >>>> >>>> This can easily happen with SD_PREFER_SIBLING enabled too so I wouldn't >>>> say that this patch breaks anything that isn't broken already. In fact >>>> we this happening with and without this patch applied. >>> >>> At least for the use case above, this doesn't happen when >>> SD_PREFER_SIBLING is set >>> >> >> On my HiKey960 I can see coscheduling on a big CPU while a LITTLE is free >> with **and** without SD_PREFER_SIBLING. Having it set only means that in >> some cases the imbalance will be re-classified as group_overloaded instead >> of group_misfit_task, so we'll skip the misfit logic when we shouldn't (this >> happens on Juno for instance). > > Can you give more details about your test case ? > I've been running the same test case as presented in the cover letter on my HiKey960 but with sched_switch tracing and with no tasksets. I've just re-run the testcase with tasksets and I get similar results (i.e. a big with coscheduling while a LITTLE is free) with or without the flag. >> >> It does nothing for the "1 task per CPU" problem that Morten described above. >> When you have this little amount of tasks, load isn't very relevant, but it >> skews the load-balancer into thinking the LITTLE CPUs are more busy than >> the bigs even though there's an idle one in the lot. >> >>>> >>>> Morten