Debugging Power Problems with Standby

  • Article

After you have developed your Modern Standby system using the proper power management guidance, you have to test and validate that the power floor is optimized to deliver great battery life in standby. You might need to break down the system to isolate a power offender.

This lab provides a deeper dive on useful tools like SleepStudy and WPA, and will guide you through various case studies that illustrate commonly encountered problems. Topics include:

  • Impact of USB devices

  • Firmware problems and missing constraints

  • Driver issues

  • Identifying spurious wake sources

Goals

This guide will show you how to perform the following tasks:

  • Interpret data from SleepStudy reports and WPA DRIPS plugins

  • Identify common issues that can impact the power floor

Terminology

  • Deepest runtime idle platform state (DRIPS): The system is said to be in DRIPS when the system is consuming the lowest amount of power possible, limited by the system’s power floor. When the screen is turned off, the Modern Standby session starts and the system goes through multiple phases to move into a low-power state. When the system is in the lowest-power state, the system is in DRIPS. The system is not in DRIPS when it is performing tasks like receiving emails, updating live tiles with fresh content, receiving VoIP calls, or any other background task that requires system resources. The more time the system spends in DRIPS before the screen is turned back on, the longer the battery life.

    Total standby session time = DRIPS time + non-DRIPS time

  • Activators: Software components that are allowed to perform work in the background while in Modern Standby.

Tools

The Windows Performance Toolkit consists of two independent tools: Windows Performance Recorder (WPR) and Windows Performance Analyzer (WPA). WPR is a powerful recording tool that creates Event Tracing for Windows (ETW) recordings. You can run WPR from the user interface (UI) or from the command line (CL). WPR provides built-in profiles that you can use to select the events you want to record. WPA is a powerful analysis tool that combines a flexible UI with extensive graphing capabilities and data tables that can be pivoted and have full text search capabilities.

SleepStudy is a Windows diagnostics tool that supports Modern Standby (connected or disconnected). It monitors a Modern Standby PC’s behavior and provides actionable diagnostics on Modern Standby battery life. It’s available only on Modern Standby capable PCs. SleepStudy generates a summary of top issues that cause poor Modern Standby battery life.

To obtain a SleepStudy report, type the following command into an Administrator Command Prompt:

powercfg.exe /SleepStudy

The built-in powercfg.exe utility will create an HTML file named sleepstudy-report.html in the current working directory.

Note   All the exercises in this guide use pre-generated SleepStudy reports, so you won't need to generate any SleepStudy reports for this guide.

Exercises

This guide consists of the following exercises.