From patchwork Fri Jul 21 15:50:10 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lukasz Luba X-Patchwork-Id: 705155 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2FACBEB64DC for ; Fri, 21 Jul 2023 15:50:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232183AbjGUPuE (ORCPT ); Fri, 21 Jul 2023 11:50:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49924 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232265AbjGUPuC (ORCPT ); Fri, 21 Jul 2023 11:50:02 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id AD69B171B; Fri, 21 Jul 2023 08:50:00 -0700 (PDT) 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 A97292F4; Fri, 21 Jul 2023 08:50:43 -0700 (PDT) Received: from e129166.arm.com (unknown [10.57.0.79]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 7F6EE3F738; Fri, 21 Jul 2023 08:49:57 -0700 (PDT) From: Lukasz Luba To: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, rafael@kernel.org Cc: lukasz.luba@arm.com, dietmar.eggemann@arm.com, rui.zhang@intel.com, amit.kucheria@verdurent.com, amit.kachhap@gmail.com, daniel.lezcano@linaro.org, viresh.kumar@linaro.org, len.brown@intel.com, pavel@ucw.cz, Pierre.Gondois@arm.com, ionela.voinescu@arm.com, mhiramat@kernel.org Subject: [PATCH v3 00/12] Introduce runtime modifiable Energy Model Date: Fri, 21 Jul 2023 16:50:10 +0100 Message-Id: <20230721155022.2339982-1-lukasz.luba@arm.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Hi all, This patch set adds a new feature which allows to modify Energy Model (EM) power values at runtime. It will allow to better reflect power model of a recent SoCs and silicon. Different characteristics of the power usage can be leveraged and thus better decisions made during task placement in EAS. It's part of feature set know as Dynamic Energy Model. It has been presented and discussed recently at OSPM2023 [3]. This patch set implements the 1st improvement for the EM. The concepts: 1. The CPU power usage can vary due to the workload that it's running or due to the temperature of the SoC. The same workload can use more power when the temperature of the silicon has increased (e.g. due to hot GPU or ISP). In such situation or EM can be adjusted and reflect the fact of increased power usage. That power increase is due to a factor called static power (sometimes called simply: leakage). The CPUs in recent SoCs are different. We have heterogeneous SoCs with 3 (or even 4) different microarchitectures. They are also built differently with High Performance (HP) cells or Low Power (LP) cells. They are affected by the temperature increase differently: HP cells have bigger leakage. The SW model can leverage that knowledge. 2. It is also possible to change the EM to better reflect the currently running workload. Usually the EM is derived from some average power values taken from experiments with benchmark (e.g. Dhrystone). The model derived from such scenario might not represent properly the workloads usually running on the device. Therefore, runtime modification of the EM allows to switch to a different model, when there is a need. 3. The EM can be adjusted after boot, when all the modules are loaded and more information about the SoC is available e.g. chip binning. This would help to better reflect the silicon characteristics. Thus, this EM modification API allows it now. It wasn't possible in the past and the EM had to be 'set in stone'. Some design details: The internal mechanisms for the memory allocation are handled internally in the EM. Kernel modules can just call the new API to update the EM data and the new memory would be provided and owned by the EM. The EM memory is used by EAS, which impacts those design decisions. The EM writers are protected by a mutex. This new runtime modified EM table is protected using RCU mechanism, which fits the current EAS hot path (which already uses RCU read lock). The unregister API handles only non-CPU (e.g. GPU, ISP) devices and uses the same mutex as EM modifiers to make sure the memory is safely freed. More detailed explanation and background can be found in presentations during LPC2022 [1][2] or in the documentation patches. The time cost to update EM for 11 OPPs can be found here [6]. It's roughly 1.5us per 1 OPP while doing this on Little CPU at max frequency (1.8GHz). Changelog: v3 - adjusted inline comments for structure doc (Dietmar) - extended patch header with infromation that only EAS will use the feature and it was driving the design (Dietmar) - changed patch header and put shorter comment (Dietmar) - moved the 'refactoring' patch that adds 'default_table' before the introduction of runtime modifiable feature as sugested by Dietmar in numerous patches v2 - merged documentation patches into one - added more explenation about the 2 tables design into the Doc (Dietmar) - removed the CPPC+EM patch for runtime modification - removed the trace patch, since the trace point would be added after a while - renamed 'tmp' to 'runtime_table' variable in the unregister function, to better highlight the memory pointer checks (it is possible after moving the 'default_table' earlier) - and added '__rcu' in the unregister function which should calm down the test bot warning - renamed 'create' to 'refactor' in the patch header (Dietmar) v2 [5]: - solved build warning of unused variable in patch 13/17 when EM is not compiled in, e.g. on Intel platform for this cpufreq_cooling - re-based on top of v6.4-rc1 v1: - implementation can be found here [4] Regards, Lukasz Luba [1] https://lpc.events/event/16/contributions/1341/attachments/955/1873/Dynamic_Energy_Model_to_handle_leakage_power.pdf [2] https://lpc.events/event/16/contributions/1194/attachments/1114/2139/LPC2022_Energy_model_accuracy.pdf [3] https://www.youtube.com/watch?v=2C-5uikSbtM&list=PL0fKordpLTjKsBOUcZqnzlHShri4YBL1H [4] https://lore.kernel.org/lkml/20230314103357.26010-1-lukasz.luba@arm.com/ [5] https://lore.kernel.org/lkml/20230512095743.3393563-1-lukasz.luba@arm.com/ [6] https://lore.kernel.org/lkml/57a5dc82-f2c9-5190-e3fa-702b2eb2de5e@arm.com/ Lukasz Luba (12): PM: EM: Refactor em_cpufreq_update_efficiencies() arguments PM: EM: Find first CPU online while updating OPP efficiency PM: EM: Refactor em_pd_get_efficient_state() to be more flexible PM: EM: Refactor a new function em_compute_costs() PM: EM: Check if the get_cost() callback is present in em_compute_costs() PM: EM: Refactor struct em_perf_domain and add default_table PM: EM: Add update_power() callback for runtime modifications PM: EM: Introduce runtime modifiable table PM: EM: Add RCU mechanism which safely cleans the old data PM: EM: Add runtime update interface to modify EM power PM: EM: Use runtime modified EM for CPUs energy estimation in EAS Documentation: EM: Update with runtime modification design Documentation/power/energy-model.rst | 150 +++++++++++++- drivers/powercap/dtpm_cpu.c | 27 ++- drivers/powercap/dtpm_devfreq.c | 23 ++- drivers/thermal/cpufreq_cooling.c | 23 ++- drivers/thermal/devfreq_cooling.c | 23 ++- include/linux/energy_model.h | 85 ++++++-- kernel/power/energy_model.c | 288 +++++++++++++++++++++++---- 7 files changed, 525 insertions(+), 94 deletions(-)