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,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 A6790C433DB for ; Wed, 17 Feb 2021 11:58:58 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 457FF6024A for ; Wed, 17 Feb 2021 11:58:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 457FF6024A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=I2wjGItyAb50iiGnTrZpUCkpEdQOhi/km9r545VEOuM=; b=1nDumyXOG3K9Y857xJdJlOLaP 6AVbqwjop4Y3tZd9iL+qF/84kJuVu0HYAgoj1OtmYBB25h1ySistRKXTVijQ0seYENnlxMY3y44Vw RgVV2Ld9bydG21+brsP4KRDZngLQohn7BO/YGKmwhiChWfRjEbg7NNcgBxeqH2sw2FNan/G43GMAK bR7gJPihOZ3/kR6wDudXHo7WuBEtcSBd8q+RhYy2mn0joCC6lgM+ck6raV7sfe0FbXuodWOiRHv9D 9yOCJtao4kIe3aA3X6IMYKlTlHX8oII2GlFpGBt3DK43xHNwc1JCi3JreEGOB8IgM7QYRQn5DTSUs YPdqp2ihQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1lCLSW-0007rW-7c; Wed, 17 Feb 2021 11:57:32 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1lCLSU-0007qQ-Cv for linux-arm-kernel@lists.infradead.org; Wed, 17 Feb 2021 11:57:31 +0000 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 854FB31B; Wed, 17 Feb 2021 03:57:28 -0800 (PST) Received: from localhost (unknown [10.1.195.40]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 24BD23F694; Wed, 17 Feb 2021 03:57:28 -0800 (PST) Date: Wed, 17 Feb 2021 11:57:26 +0000 From: Ionela Voinescu To: Viresh Kumar Subject: Re: [PATCH V3 1/2] topology: Allow multiple entities to provide sched_freq_tick() callback Message-ID: <20210217115726.GA25441@arm.com> References: <20210203114521.GA6380@arm.com> <20210205091424.3od3tme3f7mh7ebp@vireshk-i7> <20210217002422.GA17422@arm.com> <20210217042558.o4anjdkayzgqny55@vireshk-i7> <20210217113011.GA22176@arm.com> <20210217114027.ashqh67hrfk4hwib@vireshk-i7> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210217114027.ashqh67hrfk4hwib@vireshk-i7> User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210217_065730_577182_8E9A48CC X-CRM114-Status: GOOD ( 23.51 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Vincent Guittot , linux-pm@vger.kernel.org, Catalin Marinas , Rafael Wysocki , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Sudeep Holla , Will Deacon , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wednesday 17 Feb 2021 at 17:10:27 (+0530), Viresh Kumar wrote: > On 17-02-21, 11:30, Ionela Voinescu wrote: > > The problem is not topology_scale_freq_invariant() but whether a scale > > factor is set for some CPUs. > > > > Scenario (test system above): > > - "AMUs" are only supported for [1-2], > > - cpufreq_supports_freq_invariance() -> false > > > > What should happen: > > - topology_scale_freq_invariant() -> false (passed) > > - all CPUs should have their freq_scale unmodified (1024) - (failed) > > because only 2 out of 6 CPUs have a method of setting a scale factor > > > > What does happen: > > - arch_set_freq_tick() -> topology_set_freq_tick() will set a scale > > factor for [1-2] based on AMUs. This should not happen. We will end > > up with invariant signals for bigs and signals that are not freq > > invariant for littles. > > Another case. cpufreq is included as a module and AMU is implemented > partially. > > - first time cpufreq driver is inserted, we set up everything and > freq_scale gets updated on ticks. > > - remove cpufreq driver, we are back in same situation. > Yes, but the littles (lacking AMUs) would have had a scale factor set through arch_set_freq_scale() which will correspond to the last frequency change through the cpufreq driver. When removing the driver, it's unlikely that the frequency of littles will change (no driver). - topology_scale_freq_invariant() will still return true. - littles would still have a scale factor set which is likely accurate - bigs will continue updating the scale factor through AMUs. See a very useful comment someone added recently :) : """ + /* + * We don't need to handle CPUFREQ_REMOVE_POLICY event as the AMU + * counters don't have any dependency on cpufreq driver once we have + * initialized AMU support and enabled invariance. The AMU counters will + * keep on working just fine in the absence of the cpufreq driver, and + * for the CPUs for which there are no counters available, the last set + * value of freq_scale will remain valid as that is the frequency those + * CPUs are running at. + */ """ > We can't control it that way.. Or we add another call layer in middle > before the tick-handler gets called for AMU, which will check if we > are fully invariant or not ? > I would avoid additional work done on the tick, especially for a scenario which is unlikely. If you think this case is worth supporting, it might be best to do it at CPUFREQ_REMOVE_POLICY event. Thanks, Ionela. > -- > viresh _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel