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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id F230DC021A9 for ; Mon, 17 Feb 2025 15:09:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To: Content-Transfer-Encoding:Content-Type:MIME-Version:References:Message-ID: Subject:Cc: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=Av6N2v99kQHQnPnSJFrkMLTImKrQ1RUbvtaexxYCx2o=; b=BVSYjCC5la56885zXrzgxfviwo qXYHUq2ek5r0hK7+pooiSaBwWZq/8ZjO2hrTRoXiT8DtRJEaOBnK/BlyXzhxnbiW9KxhiAuyuNHML B3kUcTxa6CSb3bhEtK++B5YEWo+oaOaBfNihRJ6pbTz4CURbVmDODpwUlX/ZfGFYoZNLb1atMFWKk d6KXtaH9dkJBGTv3KAIokvPCYkVQsOoIzwkxhWKv0Mgqw62W6BLehG5Y3eyIOlkevmWLdqUMSPyVm cWQrnxXHHzPte+gBcB78gujcitNCL/7ItFSPR8uNRgwVxOmEP3JVHeG66iQnjjlaEhpIm/neX1A9A w3Dzwejg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tk2ki-00000004zYr-0XzF; Mon, 17 Feb 2025 15:09:44 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tk2ZM-00000004xgh-2UcZ for linux-arm-kernel@lists.infradead.org; Mon, 17 Feb 2025 14:58:02 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 83D1F5C580B; Mon, 17 Feb 2025 14:57:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D58F0C4CEE4; Mon, 17 Feb 2025 14:57:55 +0000 (UTC) Date: Mon, 17 Feb 2025 14:57:53 +0000 From: Catalin Marinas To: "Rafael J. Wysocki" Cc: Beata Michalska , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org, ionela.voinescu@arm.com, sudeep.holla@arm.com, will@kernel.org, viresh.kumar@linaro.org, sumitg@nvidia.com, yang@os.amperecomputing.com, vanshikonda@os.amperecomputing.com, lihuisong@huawei.com, zhanjie9@hisilicon.com, ptsm@linux.microsoft.com, Jonathan Corbet , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , Phil Auld , x86@kernel.org, linux-doc@vger.kernel.org Subject: Re: [PATCH v10 2/4] cpufreq: Introduce an optional cpuinfo_avg_freq sysfs entry Message-ID: References: <20250131162439.3843071-1-beata.michalska@arm.com> <20250131162439.3843071-3-beata.michalska@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250217_065800_709710_7E913156 X-CRM114-Status: GOOD ( 24.57 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Feb 17, 2025 at 12:52:44PM +0100, Rafael J. Wysocki wrote: > On Fri, Jan 31, 2025 at 5:25 PM Beata Michalska wrote: > > > > Currently the CPUFreq core exposes two sysfs attributes that can be used > > to query current frequency of a given CPU(s): namely cpuinfo_cur_freq > > and scaling_cur_freq. Both provide slightly different view on the > > subject and they do come with their own drawbacks. > > > > cpuinfo_cur_freq provides higher precision though at a cost of being > > rather expensive. Moreover, the information retrieved via this attribute > > is somewhat short lived as frequency can change at any point of time > > making it difficult to reason from. > > > > scaling_cur_freq, on the other hand, tends to be less accurate but then > > the actual level of precision (and source of information) varies between > > architectures making it a bit ambiguous. > > > > The new attribute, cpuinfo_avg_freq, is intended to provide more stable, > > distinct interface, exposing an average frequency of a given CPU(s), as > > reported by the hardware, over a time frame spanning no more than a few > > milliseconds. As it requires appropriate hardware support, this > > interface is optional. > > > > Note that under the hood, the new attribute relies on the information > > provided by arch_freq_get_on_cpu, which, up to this point, has been > > feeding data for scaling_cur_freq attribute, being the source of > > ambiguity when it comes to interpretation. This has been amended by > > restoring the intended behavior for scaling_cur_freq, with a new > > dedicated config option to maintain status quo for those, who may need > > it. > > In case anyone is waiting for my input here > > Acked-by: Rafael J. Wysocki > > for this and the previous patch and please feel free to route them > both through ARM64. Thanks Rafael. I indeed plan to take them through the arm64 tree. -- Catalin