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 941B0C021A9 for ; Mon, 17 Feb 2025 18:22:56 +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=xR1w2B2YW/IRMK7/rmkdjRnp6IaVcME7dFDC2bjLQYc=; b=Gp/ANZEDEAndM7VINe+6QvW0/U XfAvGvgw7LQfINagJwsOzsQRAvDDOv2WEJZVQjBqUT0SBw9qgOWUQ5ZrA12NWAtpfmlR7DLb8TPSc pAkGgAE26SdApAA+chY8hcZUzAl9tQN29MEk78ozlXMiOz1clPNVluhMCfYUSTvVItJhYV7K9TsOd aOyl1jKX7o7uRXfau7cv6BoLwWCtz1aKrc3gzjXlIv9sjlf0Sxu8ChfrVBEKV35l/T9v2syQN0kmb aE55FPaSlLuKTFP5prIkGTvCH40+1nLIIg9oTPdvaeX5j0r8cpiS4kl2MCjUmt1LnzxJ/Az7RVI5Y 4hLsVF2Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tk5lU-00000005apt-2heZ; Mon, 17 Feb 2025 18:22:44 +0000 Received: from nyc.source.kernel.org ([147.75.193.91]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tk5iy-00000005aJr-3fqN for linux-arm-kernel@lists.infradead.org; Mon, 17 Feb 2025 18:20:10 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id CDDF9A40112; Mon, 17 Feb 2025 18:18:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96C0DC4CED1; Mon, 17 Feb 2025 18:20:03 +0000 (UTC) Date: Mon, 17 Feb 2025 18:20:01 +0000 From: Catalin Marinas To: Sudeep Holla Cc: Ionela Voinescu , "Rafael J. Wysocki" , Beata Michalska , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org, 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_102009_054784_969486CA X-CRM114-Status: GOOD ( 33.04 ) 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 04:05:34PM +0000, Sudeep Holla wrote: > On Mon, Feb 17, 2025 at 03:07:24PM +0000, Ionela Voinescu wrote: > > 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. > > Ah I see it is indeed dependent. Just responded on the other thread before > reading this. So it is better if Catalin picks up [6] as well. Sorry for > the confusion. I picked that one as well. I'll do some tests and push them out later today or tomorrow morning. Thanks. -- Catalin