Longhorn Power Management Update Geralyn Miller Program Manager Mobile PC microsoft.com Microsoft Corporation Pat Stemen Program Manager Windows Kernel Platform microsoft.com Microsoft Corporation

Session Outline Longhorn Power Management Goals Extending Usage Models Reliability Configuration and Management Architectural Changes Improved User Interface Legacy Reduction

Longhorn Power Management Goals Simplify power management Enhance power management usage models Improve usability: reliability, predictability, transparency, manageability Extend power policy and state awareness system-wide Support emerging hardware, standards Enable maximum energy savings

Simplifying Power Management for Users Power schemes today are too complicated Users don’t understand scheme names, policy settings Users will not change power schemes based on usage scenario e.g., Presentation Even if they do, they are likely to forget to return to a more appropriate policy Laptop battery runs down too quickly after a presentation

Simplifying Power Management for Users Windows codenamed “Longhorn” features 3 simplified power policies Maximum power savings Trade performance to save power Automatic Let the system choose the best state based on demand Planned default for most platforms, SKUs Maximum performance Provide maximum performance at the expense of power savings Longhorn development and feedback may result in fewer power policies Additional power policies may be created IT professional, end user, OEM

New Power Management Usage Models Media PCs are driving the need for Consumer Electronics (CE) on/off models Requires fast response to user on/off requests Similar to a TV remote control PC may need to continue to operate in the background TV recording Act as a media server

New Power Management Usage Models Away mode User Present, Not Present Not a policy, but a power state Away mode attributes Blank video Mute audio Filter some input devices No power policy change – based on policy: System may remain in S0 (working) System may idle to Sleep Implementation contained completely within Windows No hardware or BIOS changes are required DPPE notifications provided for User Present/Not Present Events

New Power Management Usage Models Windows Direct Experience Platform infrastructure that launches a specific scenario or application based on the system wake source e.g., start a media player or shell when the “media” button is pressed Start from any non-working state Off or sleep states (S3-S5) Offers quick system startup Resume from Standby (S3) < 3 seconds Resume from Hibernate (S4 ) <10 seconds (Dependent on amount of physical RAM) Boot from Off (S5) ~15 seconds

New Power Management Usage Models Hybrid Sleep - Combines Standby (Suspend to RAM) and Hibernate (Suspend to Disk) Saves hibernate file, enter Standby Normally resume from memory (fast) If power is lost in Standby, system will resume using the hibernate image Enables simple shutdown metaphor Users don’t have to distinguish between Standby and Hibernate – just “Sleep” Provides increased reliability Data and system context are always preserved Eliminates S0 transition on S4 doze timeout System can simply be turned off Reduces chance of “wake in the bag and melt”

Hybrid Sleep Demonstration

Improving Reliability Failed sleep requests are a primary reliability and usability problem End user frustration – system didn’t do what the user asked Failed sleep warning messages are not a good solution Mobile lid is closed Some applications display warnings, some do not Services may silently fail sleep PC may be in a bag in some scenarios Doze to hibernate, hibernate on critical battery Battery drains, system overheats

Improving Reliability Sleep Diagnostic Agent (SDA) Project to address sleep reliability at Microsoft Data collection on real world usage of sleep states Thousands of sleep transitions from hundreds of self-host systems Instrumented OS components and data collection agent Collects both reliability and performance metrics Identifies vetoes, driver crashes, hibernate failures, etc. Tracks resume times Installs on systems with Windows XP SP2 Future plans Plan to add similar data collection components to Longhorn

Improving Reliability

SDA data shows component vetoes are most common failure 38% of all failures Applications veto more often than services and drivers Investigations show that many applications do not need to veto Potential network connectivity loss is a common cause of veto Components must handle this case outside of sleep Reducing component vetoes in Longhorn Longhorn will not always query applications or services when entering sleep Applications will only receive PBT_APMSUSPEND Can be reverted to Windows XP behavior with group policy Drivers will not be queried in some scenarios When sleep starts with lid switch, sleep button, power button Addresses scenarios where the mobile PC is in a bag and the lid is closed Critical battery, thermal conditions

Improving Reliability Kernel-mode failures are second-largest failure 26% of all failures Drivers crashing while handling power IRPs Drivers (or ACPI control methods) hanging while handling power IRPs Reducing sleep and resume kernel-mode failures in Longhorn Continue to leverage OCA Power watchdogs Aid in driver development Catch bad driver implementations before they are released Monitor power IRPs Monitor ACPI control methods run as a result of power IRP Raise system error after timeout

Improving Reliability Windows Longhorn will include diagnostics for sleep and resume transitions Run-time analysis of sleep failures User can resolve some failure cases Collect metrics Success and root cause of failure Resume and hibernate performance Report to Microsoft Windows Longhorn version of SDA data collection Success and failure reported via Service Quality Metrics (SQM) Continues goals of the Sleep Diagnostic Agent in Longhorn Failure trace logs reported via Windows Error Reporting (WER) Post-failure analysis at Microsoft Response can be provided to the user for software update

Power Management Configuration Advancements Very important to enterprise customers Easy configuration to reduce energy consumption Opportunity to save money and the environment Technologies Group Policy control of power settings Works for non domain-joined systems Admin can limit or control user’s settings Robust command-line tool (powercfg) for script use Separate policy for “no user logged in” Offline power policy editing New permissions model No longer need Admin rights to change policy

Extending Power Policy and State Device Power Policy Engine Enables additional generic device support participation Beyond run time idle power management Extends policy, state to drivers, applications Kernel mode and USER mode interfaces Integrates device power management support Allows for custom device power controls Stores device policy data

Extending Power Policy and State Device Power Policy Engine Provides power event notifications, eliminating polling System power state (AC or DC) Power policy change Monitor On/Off User Present/Unattended Disk spin up Battery level change

Architectural Changes Kernel Power Manager New policy data store GUID-based All policy stored per-user No more User, Machine, Global, etc. WDM power simplifications Detailed in future white paper

Architectural Changes Processor Power Management Re-designed kernel interface, processor drivers Native support for multi-processor coordination Domain dependency support Consolidated policy state machine Eliminate processor throttling policies Enable behavior handler(s) for p-states Optimize C-state algorithms Constrain use of linear throttle states

InstantON Architecture Enhanced memory management Mitigate risk of page faults in resume path Consistent and fast resume performance Even after system reboot Improved hibernate resume times Fast application launch with Windows Direct Experience Continue kernel power manager improvements, resiliency Parallelism, IRP dispatch, fewer blocking paths Updated USB hub driver

Enhanced Power Savings Optimized use of processor power management Performance states, Idle sleep states Enable support for additional devices GPU, wireless NIC, optical drives, etc. Extend awareness to software layers Shell, applications Incorporate screen brightness into policy Enhanced HDD power management Keep HDD off longer once spun down

Improved User Experience Simplified shutdown UI Better diagnostics Improved battery meter Additional OEM extensibility points Intelligent defaults for power scheme settings

Improved User Experience Simplified shutdown UI Move to appliance-like Power button Promote Sleep as the default off state

Improved User Experience Diagnostics Goal: All power transitions should “just work” Streamlined Shutdown Once countdown timer expires, shutdown occurs immediately Only applications that users care about will be able to block Users will have the ability to override blocking applications Disabled Standby States #1 cause: legacy drivers Users will receive message and can update, disable or uninstall drivers

Improved User Experience Improved Battery Meter Timely battery notifications – no more stale alarms On-hover UI provides at-a-glance information First tier UI provides quick, easy way to switch between power plans

New Opportunities for OEM Extensibility Extend the Battery Meter user experience Expose time/% remaining and active power plan via the on-hover UI Expose customized power plans via the first-tier UI Launch custom power applets from the context menu Extend the Control Panel user experience DPPE power settings are automatically exposed to the advanced user Eliminates need to build custom property sheets

Improved User Experience Improved User Experience Power scheme settings AdaptiveMax P-StateAdaptive Min P-StateAdaptive Processor Throttling 240 minnever240 minnever240 min S4 Doze Timeout 60 minNever60 min 15 min60 min Idle Time Sleep Idle Action 20 min 10 min20 min5 min20 min HDD Spindown _BCL(1)_BCL(0)_BCL(1)_BCL(0)_BCL(1)_BCL(0) Display Brightness 20 min 5 min20 min3 min20 min Monitor Blank DCACDCACDCAC Max PerformanceAutomaticMax BatteryParameter

Legacy Reduction Longhorn will only boot on ACPI systems Retired support for: Advanced Power Management (APM) EISA bus support Hardware Profiles ISAPnP (not installed by default)

Legacy Reduction Retired legacy processor drivers amdk6.sys – Supported the AMD K6/2+ Mobile Processor p3.sys – Supported the Mobile Intel Pentium III legacy SpeedStep detection interfaces The Mobile Intel Pentium III with SpeedStep is still supported via the ACPI 2.0 processor objects Removed legacy processor performance state detection and enumeration interfaces Retired the Processor Driver Kit (PDK) Only applicable to CPU manufacturers Removed the serial UPS service

Call To Action Design and test for sleep and fast resume Be aware of query behavior changes in Windows Longhorn Review power group policy support

Community Resources Windows Hardware & Driver Central (WHDC) Technical Communities Non-Microsoft Community Sites Microsoft Public Newsgroups Technical Chats and Webcasts Microsoft Blogs

Additional Resources Web Resources Windows Hardware and Driver Central: PnP, Power Management, WMI: Windows Power Management (OnNow) Related Sessions “Building a Longhorn-Ready Mobile PC” “Goodbye SMI – ACPI and Graphics Driver/System Firmware Interface” microsoft.com

© 2005 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.