From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 47E1B224B02; Mon, 17 Feb 2025 14:57:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739804280; cv=none; b=Dtk/zToRZ5MXsf+qx69L2P5xZBkRuIVPzbR0IJIn4gq/gnMLBlULER6rrz2gjTEKyNq33dYcaJUplm5A+RY72K/mOVTPXBMiQNmILwwZ1o6/vWBSbSTTGc/EdmofpKD+AyBA2RXyxeAFpVKSw6UMkTiZTbYITWRrUyAV9NEgkfU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739804280; c=relaxed/simple; bh=i5qIBPFIfSleKeqPnmWgDXFsvCA3yOtMTPrnhYV6Cqs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=I5rO2SYwjHeE7QXaUxO1ge8gT+ZOpkHWAjerKGO2j0XbtJywaxhm3npOLSTkNHWfVffSxOMD+KSRSRs9Nqs/0C1BCLuCOQtIJ0VyLcDvI6kpyG4r8nD3AXWjhdVaPainUmVNjn4nh5ZDnm+zxrA0AbEUMvHwUbgbV0W4wbjlJCg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 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> Precedence: bulk X-Mailing-List: linux-pm@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: 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