From patchwork Mon Oct 19 14:05:59 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lukasz Luba X-Patchwork-Id: 11844435 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=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,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 E1B62C43457 for ; Mon, 19 Oct 2020 14:08:07 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 71D2922263 for ; Mon, 19 Oct 2020 14:08:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="czTNmc4A" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 71D2922263 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:MIME-Version:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:References:In-Reply-To:Message-Id:Date:Subject:To: From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=fo73TVi/ZcnX24Tq8oeDkAIdDqjdwbVjbtAzlwGtJpI=; b=czTNmc4A1pIkodPKjHZo6oMnCP LeXZ0w9kca5AupBjK3GLYLEHCdyrGALsfLsX0IC/uj50JpEf04baODEVxGvG/OaJHdGJFAGED5OMu NXkNGfxO8H9S7Q4t63UIspP+btkEbmKB9+fGZjBsEJnkBfdJPkSWYFpaIdhUZdgbFrP6oJ6TF61eX k5HpEJbPgPEU7MqAFA+vxG5SipowQDsRiTUP1lkEtIXdbG6xXe3S5pX+VkOfUQGmAeRraVOHcsVJa D8VDvFk0KYpatZfUHuB35Ku/wayJ01OeCaCteNz/Qf8m/BMiXsNJCbtxGCQEJkdgx0hymgKXT2rcJ yHws7Y8A==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kUVo3-0003yr-1R; Mon, 19 Oct 2020 14:06:35 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kUVny-0003xb-Vy for linux-arm-kernel@lists.infradead.org; Mon, 19 Oct 2020 14:06:32 +0000 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 2DFAAD6E; Mon, 19 Oct 2020 07:06:30 -0700 (PDT) Received: from e123648.arm.com (unknown [10.57.15.200]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 81FAA3F66E; Mon, 19 Oct 2020 07:06:25 -0700 (PDT) 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 Subject: [PATCH v3 2/4] docs: Clarify abstract scale usage for power values in Energy Model Date: Mon, 19 Oct 2020 15:05:59 +0100 Message-Id: <20201019140601.3047-3-lukasz.luba@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20201019140601.3047-1-lukasz.luba@arm.com> References: <20201019140601.3047-1-lukasz.luba@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201019_100631_210055_7BD2DC1E X-CRM114-Status: GOOD ( 16.25 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: nm@ti.com, rafael@kernel.org, daniel.lezcano@linaro.org, rnayak@codeaurora.org, corbet@lwn.net, sboyd@kernel.org, viresh.kumar@linaro.org, mka@chromium.org, amitk@kernel.org, dianders@chromium.org, morten.rasmussen@arm.com, robh+dt@kernel.org, sudeep.holla@arm.com, qperret@google.com, Dietmar.Eggemann@arm.com, lukasz.luba@arm.com MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.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 | 13 ++++++++++++- Documentation/power/energy-model.rst | 13 +++++++++++++ Documentation/scheduler/sched-energy.rst | 5 +++++ 3 files changed, 30 insertions(+), 1 deletion(-) diff --git a/Documentation/driver-api/thermal/power_allocator.rst b/Documentation/driver-api/thermal/power_allocator.rst index 67b6a3297238..b7992ae84fef 100644 --- a/Documentation/driver-api/thermal/power_allocator.rst +++ b/Documentation/driver-api/thermal/power_allocator.rst @@ -71,7 +71,10 @@ 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. This is the case when the Energy Model +provides the power values 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 +272,11 @@ 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 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^