Andrew WhitechapelProgram ManagerMemory and CPU Policy in Univeral Apps

Expand Your Reach by Tuning for Memory and CPU Policies

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Why do I care?What does policy cover?Why does the system do this?How does policy vary per SKU or device?Show me the code

Agenda slide

• I can make my app scale across multiple devices and SKUs

• I can make my app resilient to ongoing conditions• Hardware, connectivity, state changes

• My app doesn’t show up on the battery wall of shame

• My app doesn’t crash or cause the device to become unusable

• I can use a rich set of features without degrading the system

Why do I care?

• Resources are finite• Maintaining an optimal balance• Different strokes for different task types• Mapping scenario priority to resource

sets• Achieving predictability• Allow apps to understand and

cooperate in the running ecosystem• Adjusting dynamically

Why does the system do this?

• Policy is holistic• Memory• CPU and task lifetime• User expectations and scenario

prioritization• Gated access to sensors• Other constraints

What does policy cover?

Memory breakdown examples 94% of apps

peak at <150MB.

92% of apps average at <100MB.

Component usage (ballpark)512MB Phone

1GB Tablet

2GB Desktop

Total physical 512 1024 2048

Paging level 200 200 1600

  712 1224 3648

BSP, OS, drivers, services 425 425 425

OEM/MO service agents 22 40  

VOIP or Background audio 66 80 80

VPN 10 10 20

  523 555 525

Foreground App 185 390 900Back-stack, Task completion, BG tasks, More FG apps 4 279 2223

Different strokes

Task typeMemory Cap MB

Lifetime CPU

Block in Batt-Sav

Default Background Task 16 30 sec 10% Y

Long-Running Bluetooth 16 ∞ 10% Y

Extended Execution 150 10 min 10% YBackground Audio Playback 25 ∞ 10% N

VOIP Active Call 66 ∞ 70% N

Modern Foreground App 185 ∞ 70% N

Example: 512MB

device

• Scenario-based prioritization.

Task Priorities

*Higher priority if part of the Foreground experience.

Task type Priority

Foreground App 2

VOIP 2

Background Audio 2

VPN 2

Background Transfer 2 or 6*

Bluetooth 3CachedFileUpdater/ShareDataPackage Task 3 or 6*

Task Completion 4

Geofence-triggered Task 5

Default Background Tasks 6

App in the backstack 7

Example: Background Audio Agent

Sensor resources

Resource Allowed?

Microphone Camera Proximity Gyro Compass Accelerometer Vibrator Push SpeechSynthesis SpeechRecognition Audio InterruptiveUI

• Protected sensor resources• MemoryManager API• EnergyManager API

Show me the code

Sensor Resource APIsNetworkInformation.NetworkStatusChanged += OnNetworkStatusChanged;Battery.AggregateBattery.ReportUpdated += OnBatteryReportUpdated; ;

bool isGyro = Gyrometer.GetDefault() != null;bool isAccelero = Accelerometer.GetDefault() != null;bool isCompass = Compass.GetDefault() != null;MediaCapture mediaCapture = new MediaCapture();bool isCamera = mediaCapture != null;

BatteryReport batteryReport = Battery.AggregateBattery.GetReport();if (batteryReport.Status != BatteryStatus.NotPresent){ int charge = (int)batteryReport.RemainingCapacityInMilliwattHours;}

ConnectionProfile profile = NetworkInformation.GetInternetConnectionProfile();ConnectionCost cost = profile.GetConnectionCost();if (cost.Roaming || cost.OverDataLimit) ; // prompt for user opt-in.else if (cost.ApproachingDataLimit) ; // throttle behavior.

MemoryManager APIsMemoryManager.AppMemoryUsageIncreased += OnAppMemoryUsageIncreased;MemoryManager.AppMemoryUsageDecreased += OnAppMemoryUsageDecreased;

ulong usageLimit = MemoryManager.AppMemoryUsageLimit;ulong usage = MemoryManager.AppMemoryUsage;ulong headroom = usageLimit - usage;

AppMemoryReport appReport = MemoryManager.GetAppMemoryReport();ulong privateCommit = appReport.PrivateCommitUsage;ulong peakPrivate = appReport.PeakPrivateCommitUsage;ulong totalCommit = appReport.TotalCommitUsage;ulong commitLimit = appReport.TotalCommitLimit;

ProcessMemoryReport processReport = MemoryManager.GetProcessMemoryReport();ulong privateSet = processReport.PrivateWorkingSetUsage;ulong totalSet = processReport.TotalWorkingSetUsage;

EnergyManager APIsBackgroundEnergyManager.RecentEnergyUsageIncreased += OnRecentEnergyUsageIncreased;BackgroundEnergyManager.RecentEnergyUsageReturnedToLow += OnRecentEnergyUsageReturnedToLow;

uint usage = BackgroundEnergyManager.RecentEnergyUsage;

uint usageLevel = BackgroundEnergyManager.RecentEnergyUsageLevel;if (usageLevel == BackgroundEnergyManager.NearTerminationUsageLevel) ;// Get ready to be terminated.else if (usageLevel == BackgroundEnergyManager.ExcessiveUsageLevel) ;// Throttle back urgently.else if (usageLevel == BackgroundEnergyManager.MaxAcceptableUsageLevel) ;// On the wall of shame.else if (usageLevel == BackgroundEnergyManager.NearMaxAcceptableUsageLevel) ;// Approaching the wall of shame.else if (usageLevel == BackgroundEnergyManager.LowUsageLevel) ;// Good citizen.

• Variation by SKU• Mobile vs Desktop vs HoloLens vs IoT vs Xbox

• Variation by device• Physical RAM, Pagefile, Screen resolution

• Variation by app technology• Universal apps, pre-Windows 10 Phone, pre-Windows

10 Modern Desktop, Win32

How does policy vary?

• Target a wide range of SKUs and devices

• Query the system to discover your constraints

• Listen for change events• Tune your behavior accordingly

What’s the moral of the story?

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