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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 39E90C001DF for ; Mon, 24 Jul 2023 17:57:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231738AbjGXR5K (ORCPT ); Mon, 24 Jul 2023 13:57:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55496 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229597AbjGXR4w (ORCPT ); Mon, 24 Jul 2023 13:56:52 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 93FBC4C0C for ; Mon, 24 Jul 2023 10:54:57 -0700 (PDT) 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 2E05CFEC; Mon, 24 Jul 2023 10:55:40 -0700 (PDT) Received: from [192.168.178.6] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2B7453F5A1; Mon, 24 Jul 2023 10:54:56 -0700 (PDT) Message-ID: <1e675286-b4b8-5abd-dd4c-3f2ffdaf12c1@arm.com> Date: Mon, 24 Jul 2023 19:54:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [RFC PATCH] sched/fair: Fix impossible migrate_util scenario in load balance Content-Language: en-US To: Qais Yousef Cc: Vincent Guittot , Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org References: <20230716014125.139577-1-qyousef@layalina.io> <20230718161829.ws3vn3ufnod6kpxh@airbuntu> <20230718172522.s4gcfx3ppljwbks7@airbuntu> <20230721105711.nzunqdtdaevmrgyg@airbuntu> <20230721220430.qv6eqo4dosfrsilo@airbuntu> <20230724161038.nreywdwayiq2ypty@airbuntu> From: Dietmar Eggemann In-Reply-To: <20230724161038.nreywdwayiq2ypty@airbuntu> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24/07/2023 18:10, Qais Yousef wrote: > On 07/24/23 14:58, Dietmar Eggemann wrote: >> On 22/07/2023 00:04, Qais Yousef wrote: >>> On 07/21/23 15:52, Vincent Guittot wrote: >>>> Le vendredi 21 juil. 2023 à 11:57:11 (+0100), Qais Yousef a écrit : >>>>> On 07/20/23 14:31, Vincent Guittot wrote: [...] > So I actually moved everything to a single cluster and this indeed solves the > lb() issue. But then when I tried to look at DT mainline I saw that the DTs > still define separate cluster for each uArch, and this got me confused whether > I did the right thing or not. And made me wonder whether the fix is to change > DT or port Sudeep's/Ionela's patch? IMHO, you have to change DT. > I did some digging and I think the DT, like the ones in mainline by the look of > it, stayed the way it was historically defined. This would be a "mistake" for Arm DynamIQ based systems. We use QC RB5 in our testing and this board schedules only within a MC sched domain (I guess it's: arch/arm64/boot/dts/qcom/qrb5165-rb5.dts -> sm8250.dtsi) > So IIUC the impacts are on system pre-simplified EM (should have been phased > out AFAIK). And on different presentation on sysfs topology which can > potentially break userspace deps, right? I think this is not a problem too, but > can be famous last words as usual :-) The only thing I remember was when we hinted at this issue to Android folks a couple of years ago, they said they have to stay with the phantom domain due to dependencies from vendor specific code other than related to the EM. IMHO, for Pixel6 the DT cpu-map information is in: private/gs-google/arch/arm64/boot/dts/google/gs101-cpu.dtsi of the android-kernel. [...]