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 1A227C021A9 for ; Mon, 17 Feb 2025 15:17:20 +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=5ra4TmGG0IficxwdjGO3iGCFOYHeKYguQNOrpjgu7S8=; b=LeH6deIhrwJt66D37Ahxb5VS5Q bTJMKbEa4ycoqSp6h871+OF+CQi9XR1ABQ8GN/OOyjWbvVQStGEL8SPmO7v4/SilTBa6w6U6UwKK4 IOAdacWxldP4W0ZC4klAMTrTBQ0dIFXw4+61PfDf5oHPCS75KOUToKVXsrEdd01S8nncwxebJ+9rj Ntpox3x/xoEy/DTdw6LZgPc0YWqAq7PaLshQtdFY7nt368kzlfDpqxjP+IlkkdFP5ZBdLWB4aZl5N G3zafut370o6bwlxzTOF7n8n1WoNszPfRech5D0mHHi8SeyLLsDrSA1TfPA6f/y542Fdth1PlF9wX QoBflJvw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tk2rs-000000050ct-0ccW; Mon, 17 Feb 2025 15:17:08 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tk2iV-00000004zGr-124K for linux-arm-kernel@lists.infradead.org; Mon, 17 Feb 2025 15:07:29 +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 85D27152B; Mon, 17 Feb 2025 07:07:45 -0800 (PST) Received: from localhost (ionvoi01-desktop.cambridge.arm.com [10.2.80.58]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E99733F6A8; Mon, 17 Feb 2025 07:07:25 -0800 (PST) Date: Mon, 17 Feb 2025 15:07:24 +0000 From: Ionela Voinescu To: Catalin Marinas Cc: "Rafael J. Wysocki" , Beata Michalska , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org, 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_070727_330246_C7D38F14 X-CRM114-Status: GOOD ( 29.05 ) 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 Hi Catalin, On Monday 17 Feb 2025 at 14:57:53 (+0000), Catalin Marinas wrote: > 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. Just a mention that this set depends on the patch that Beata linked at [6]. That patch applies cleanly on next-20250217 and it still builds/boots/works as expected. Thanks, Ionela. > > -- > Catalin