From patchwork Tue Nov 3 09:05:58 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lukasz Luba X-Patchwork-Id: 315230 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7FC25C388F7 for ; Tue, 3 Nov 2020 09:06:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4E338223BF for ; Tue, 3 Nov 2020 09:06:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727821AbgKCJG3 (ORCPT ); Tue, 3 Nov 2020 04:06:29 -0500 Received: from foss.arm.com ([217.140.110.172]:44730 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727787AbgKCJG0 (ORCPT ); Tue, 3 Nov 2020 04:06:26 -0500 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 C428F139F; Tue, 3 Nov 2020 01:06:25 -0800 (PST) Received: from e123648.arm.com (unknown [10.57.19.30]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 433DD3F719; Tue, 3 Nov 2020 01:06:21 -0800 (PST) From: Lukasz Luba To: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-doc@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: robh+dt@kernel.org, amitk@kernel.org, corbet@lwn.net, daniel.lezcano@linaro.org, lukasz.luba@arm.com, Dietmar.Eggemann@arm.com, morten.rasmussen@arm.com, qperret@google.com, dianders@chromium.org, mka@chromium.org, rnayak@codeaurora.org, rafael@kernel.org, sudeep.holla@arm.com, viresh.kumar@linaro.org, sboyd@kernel.org, nm@ti.com Subject: [PATCH v4 2/4] docs: Clarify abstract scale usage for power values in Energy Model Date: Tue, 3 Nov 2020 09:05:58 +0000 Message-Id: <20201103090600.29053-3-lukasz.luba@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20201103090600.29053-1-lukasz.luba@arm.com> References: <20201103090600.29053-1-lukasz.luba@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org The Energy Model (EM) can store power values in milli-Watts or in abstract scale. This might cause issues in the subsystems which use the EM for estimating the device power, such as: - mixing of different scales in a subsystem which uses multiple (cooling) devices (e.g. thermal Intelligent Power Allocation (IPA)) - assuming that energy [milli-Joules] can be derived from the EM power values which might not be possible since the power scale doesn't have to be in milli-Watts To avoid misconfiguration add the needed documentation to the EM and related subsystems: EAS and IPA. Signed-off-by: Lukasz Luba --- .../driver-api/thermal/power_allocator.rst | 12 +++++++++++- Documentation/power/energy-model.rst | 13 +++++++++++++ Documentation/scheduler/sched-energy.rst | 5 +++++ 3 files changed, 29 insertions(+), 1 deletion(-) diff --git a/Documentation/driver-api/thermal/power_allocator.rst b/Documentation/driver-api/thermal/power_allocator.rst index 67b6a3297238..aa5f66552d6f 100644 --- a/Documentation/driver-api/thermal/power_allocator.rst +++ b/Documentation/driver-api/thermal/power_allocator.rst @@ -71,7 +71,9 @@ to the speed-grade of the silicon. `sustainable_power` is therefore simply an estimate, and may be tuned to affect the aggressiveness of the thermal ramp. For reference, the sustainable power of a 4" phone is typically 2000mW, while on a 10" tablet is around 4500mW (may vary -depending on screen size). +depending on screen size). It is possible to have the power value +expressed in an abstract scale. The sustained power should be aligned +to the scale used by the related cooling devices. If you are using device tree, do add it as a property of the thermal-zone. For example:: @@ -269,3 +271,11 @@ won't be very good. Note that this is not particular to this governor, step-wise will also misbehave if you call its throttle() faster than the normal thermal framework tick (due to interrupts for example) as it will overreact. + +Energy Model requirements +========================= + +Another important thing is the consistent scale of the power values +provided by the cooling devices. All of the cooling devices in a single +thermal zone should have power values reported either in milli-Watts +or scaled to the same 'abstract scale'. diff --git a/Documentation/power/energy-model.rst b/Documentation/power/energy-model.rst index a6fb986abe3c..ba7aa581b307 100644 --- a/Documentation/power/energy-model.rst +++ b/Documentation/power/energy-model.rst @@ -20,6 +20,19 @@ possible source of information on its own, the EM framework intervenes as an abstraction layer which standardizes the format of power cost tables in the kernel, hence enabling to avoid redundant work. +The power values might be expressed in milli-Watts or in an 'abstract scale'. +Multiple subsystems might use the EM and it is up to the system integrator to +check that the requirements for the power value scale types are met. An example +can be found in the Energy-Aware Scheduler documentation +Documentation/scheduler/sched-energy.rst. For some subsystems like thermal or +powercap power values expressed in an 'abstract scale' might cause issues. +These subsystems are more interested in estimation of power used in the past, +thus the real milli-Watts might be needed. An example of these requirements can +be found in the Intelligent Power Allocation in +Documentation/driver-api/thermal/power_allocator.rst. +Important thing to keep in mind is that when the power values are expressed in +an 'abstract scale' deriving real energy in milli-Joules would not be possible. + The figure below depicts an example of drivers (Arm-specific here, but the approach is applicable to any architecture) providing power costs to the EM framework, and interested clients reading the data from it:: diff --git a/Documentation/scheduler/sched-energy.rst b/Documentation/scheduler/sched-energy.rst index 001e09c95e1d..afe02d394402 100644 --- a/Documentation/scheduler/sched-energy.rst +++ b/Documentation/scheduler/sched-energy.rst @@ -350,6 +350,11 @@ independent EM framework in Documentation/power/energy-model.rst. Please also note that the scheduling domains need to be re-built after the EM has been registered in order to start EAS. +EAS uses the EM to make a forecasting decision on energy usage and thus it is +more focused on the difference when checking possible options for task +placement. For EAS it doesn't matter whether the EM power values are expressed +in milli-Watts or in an 'abstract scale'. + 6.3 - Energy Model complexity ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ From patchwork Tue Nov 3 09:06:00 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lukasz Luba X-Patchwork-Id: 315229 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0E429C4742C for ; Tue, 3 Nov 2020 09:06:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D061720756 for ; Tue, 3 Nov 2020 09:06:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727923AbgKCJGo (ORCPT ); Tue, 3 Nov 2020 04:06:44 -0500 Received: from foss.arm.com ([217.140.110.172]:44776 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727787AbgKCJGg (ORCPT ); Tue, 3 Nov 2020 04:06:36 -0500 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 CAFCB139F; Tue, 3 Nov 2020 01:06:35 -0800 (PST) Received: from e123648.arm.com (unknown [10.57.19.30]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 409B03F719; Tue, 3 Nov 2020 01:06:31 -0800 (PST) From: Lukasz Luba To: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-doc@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: robh+dt@kernel.org, amitk@kernel.org, corbet@lwn.net, daniel.lezcano@linaro.org, lukasz.luba@arm.com, Dietmar.Eggemann@arm.com, morten.rasmussen@arm.com, qperret@google.com, dianders@chromium.org, mka@chromium.org, rnayak@codeaurora.org, rafael@kernel.org, sudeep.holla@arm.com, viresh.kumar@linaro.org, sboyd@kernel.org, nm@ti.com Subject: [PATCH v4 4/4] docs: power: Update Energy Model with new flag indicating power scale Date: Tue, 3 Nov 2020 09:06:00 +0000 Message-Id: <20201103090600.29053-5-lukasz.luba@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20201103090600.29053-1-lukasz.luba@arm.com> References: <20201103090600.29053-1-lukasz.luba@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Update description and meaning of a new flag, which indicates the type of power scale used for a registered Energy Model (EM) device. Reviewed-by: Quentin Perret Signed-off-by: Lukasz Luba --- Documentation/power/energy-model.rst | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/Documentation/power/energy-model.rst b/Documentation/power/energy-model.rst index ba7aa581b307..60ac091d3b0d 100644 --- a/Documentation/power/energy-model.rst +++ b/Documentation/power/energy-model.rst @@ -30,6 +30,8 @@ These subsystems are more interested in estimation of power used in the past, thus the real milli-Watts might be needed. An example of these requirements can be found in the Intelligent Power Allocation in Documentation/driver-api/thermal/power_allocator.rst. +Kernel subsystems might implement automatic detection to check whether EM +registered devices have inconsistent scale (based on EM internal flag). Important thing to keep in mind is that when the power values are expressed in an 'abstract scale' deriving real energy in milli-Joules would not be possible. @@ -86,7 +88,7 @@ Drivers are expected to register performance domains into the EM framework by calling the following API:: int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states, - struct em_data_callback *cb, cpumask_t *cpus); + struct em_data_callback *cb, cpumask_t *cpus, bool milliwatts); Drivers must provide a callback function returning tuples for each performance state. The callback function provided by the driver is free @@ -94,6 +96,10 @@ to fetch data from any relevant location (DT, firmware, ...), and by any mean deemed necessary. Only for CPU devices, drivers must specify the CPUs of the performance domains using cpumask. For other devices than CPUs the last argument must be set to NULL. +The last argument 'milliwatts' is important to set with correct value. Kernel +subsystems which use EM might rely on this flag to check if all EM devices use +the same scale. If there are different scales, these subsystems might decide +to: return warning/error, stop working or panic. See Section 3. for an example of driver implementing this callback, and kernel/power/energy_model.c for further documentation on this API. @@ -169,7 +175,8 @@ EM framework:: 37 nr_opp = foo_get_nr_opp(policy); 38 39 /* And register the new performance domain */ - 40 em_dev_register_perf_domain(cpu_dev, nr_opp, &em_cb, policy->cpus); - 41 - 42 return 0; - 43 } + 40 em_dev_register_perf_domain(cpu_dev, nr_opp, &em_cb, policy->cpus, + 41 true); + 42 + 43 return 0; + 44 }