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=-5.2 required=3.0 tests=BAYES_00, 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 8D8EAC4741F for ; Thu, 5 Nov 2020 15:46:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 41E562151B for ; Thu, 5 Nov 2020 15:46:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731089AbgKEPqP (ORCPT ); Thu, 5 Nov 2020 10:46:15 -0500 Received: from foss.arm.com ([217.140.110.172]:35914 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730721AbgKEPqP (ORCPT ); Thu, 5 Nov 2020 10:46:15 -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 8A71C14BF; Thu, 5 Nov 2020 07:46:14 -0800 (PST) Received: from localhost (unknown [10.1.198.32]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1CA483F718; Thu, 5 Nov 2020 07:46:14 -0800 (PST) Date: Thu, 5 Nov 2020 15:46:12 +0000 From: Ionela Voinescu To: Vincent Guittot Cc: Nicola Mazzucato , Viresh Kumar , linux-kernel , LAK , "open list:THERMAL" , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Sudeep Holla , "Rafael J. Wysocki" , Viresh Kumar , Rob Herring , Stephen Boyd , Nishanth Menon , Daniel Lezcano , Morten Rasmussen , Chris Redpath Subject: Re: [PATCH v3 0/3] CPUFreq: Add support for cpu performance dependencies Message-ID: <20201105154612.GA17891@arm.com> References: <20201102120115.29993-1-nicola.mazzucato@arm.com> <20201103101840.yrgwmcjrnjn7n5q6@vireshk-i7> <87558fa9-a4c6-38c9-bcc5-f736c0229f56@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Hi guys, On Thursday 05 Nov 2020 at 15:25:53 (+0100), Vincent Guittot wrote: [..] > > > - Because of hardware co-ordination of otherwise co-ordinated CPUs, > > > few things break. Thermal and EAS are some of the examples and so > > > you are trying to fix them here by proving them the missing > > > information again. > > > > Correct. And for this I have proposed two ways. > > > > > > > > - One other thing that breaks with this is freq-invariance in the > > > scheduler, as the scheduler won't see the real frequencies the > > > various CPUs are running at. Most of the hardware we have today > > > doesn't have counters, like AMUs, not sure if all future ones based > > > on SCMI will have that too, so how are they gong to be fixed ? > > > > > > > Correct. freq-invariance without counters is trying to do its best based on the > > information it has available. It definitely relies on the knowledge of the v/f > > domains to work at its best so I think in the case of per-cpu it will follow the > > same approach as others being affected (EAS, thermal). > > As frequency invariance has same problem as EAS and Thermal it would > be good to see the solution as part of this proposal like EAS and > Thermal > I think I was waiting for a consensus on patch 3/3, although I believe the discussion at [1] tended towards option 2: "each driver to store internally the performance dependencies and let the driver directly provide the correct cpumask for any consumer." The alternative was option 1: "add a new dependent_cpus cpumaks in cpufreq_policy", as Nicola mentioned in the commit message for 3/3. If the choice is clear, I'm happy to take the FIE fixes in a separate set. Thanks, Ionela. [1] https://lore.kernel.org/linux-arm-kernel/20200924095347.32148-3-nicola.mazzucato@arm.com/ > > > > > And if we even have to fix this (freq invariance), what's hardware > > > coordination giving us that makes all this worth it ? > > > > I suppose this is more a generic question for all the platforms running with h/w > > coordination, but for our case is that the f/w will take care of the performance > > optimizations for us :) > > > > > > > > Sorry about the long list :) > > > > No problem at all. Thank you for your time on this and I hope I have made bits > > clearer. > > > > Nicola > > > > >