From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 3117B20328; Mon, 17 Feb 2025 15:07:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739804849; cv=none; b=uVPzvAGL8RzkaTyrQyD/jf6sPcsu0yQq2fMLs3U2/gMFP1CA6CIYGdT3EPZD2OgyqtVsJGi9rLwiwWvtSyepc3nb+SG3scnuqAoErzUcIRSfR4X5K10hyarWIwi6eVUNdMQ3WWNVyXUm549QkfwzEeeCTeXNDuMhAOaOlDunaIM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739804849; c=relaxed/simple; bh=/iaROEQ65LiIXoXHU4T1XaPliS7CuaEWwUdB6Rvy++k=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Zwilb0Vwj3AfKAXN63A+7pKlVVZALc2coXs7y9qdpUi/SvF+GBSscM7504pFURxyxJyuZo5h5VNV6h8ZPsE7quAaOq+tSQ9Zp876WgKHUdSEbNZPnWyECTGAQHpnHDzaJA8LzlNyUMGOC+/rXPcZFwG9Oj1/WErwDaCBHQ1gE0s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: 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