Low memory and hardware constraints

2. Low memory and hardware constraints Andrew Whitechapel Program Manager, Windows Phone Division 2-221

3. Agenda • Why do you care? • Choices for optimizing your reach. • Windows Phone resource manager. • Best practices.

4. Why do you care? • The Windows Phone SDK is a powerful toolset – use it wisely. • Make your app available on the widest range of WP devices possible. • Ensure users have a great experience with your app on all devices, and at all times. • Memory/hardware constraints can make this an interesting challenge. • A desktop OS, and desktop frameworks, on a phone. • We did work to scale to devices; now it’s your turn. • Apps live in an ecosystem on the phone.

5. Your choices for optimizing your reach • There’s more than one way to slice a lemon. • Breadth targeting. • Selective targeting. • Feature light-up and tuning. • Broad multi-targeting.

6. Breadth targeting (everything) • Aim for the lowest common denominator. • Eliminate non-universal features/capabilities/memory usage. • Simplest, most robust approach. • Sacrifice some features.

7. Selective targeting (a subset) • Via OS/platform version. • Single or multiple app versions. • Regional/market targeting. • Via device capabilities ID_CAP* and requirements ID_REQ*. • Sensors. • Memory.

8. Feature light-up and tuning • Conditionally enable/disable features. • Allow for chassis/platform variation. • IsSupported. • IsXXXSupported. • Reflection: tiles and in-app purchase. • Static versus dynamic. • ID_REQ_MAGNETOMETER versus Compass.IsSupported.

9. Check for optional features • Fixed (per device) and dynamic (per user selection).

10. Tile light-up • Reflection is a two-edged sword. • Enhanced tiles: compile for WP7, light-up in WP8. • Rudy Huyn: http://mangopollo.codeplex.com/

11. Windows Phone resource management • The ResMan mandate: maintain an optimal user experience across all scenarios. • Memory quotas and caps. • CPU quotas and caps. • Sensor resources. • Paging: the pros and cons. • Why do caps vary by app type? • Requesting a higher cap; and the implications.

12. Memory cap defaults • Caps are not quotas. • Certification 5.25: “An app must not exceed 90 MB of RAM usage, except on devices that have more than 256 MB of memory.” • 95% of apps use <150MB. *Cannot run concurrently with VOIP.

13. Memory cap breakdown • Juggling behind the scenes. • “Worst case” != “common case”.

14. Memory cap breakdown

15. Best practices • See Stefan Wick’s talk: 2-216, Friday 10:30. • Building for scale enforces discipline. • Use memory APIs to check your usage (debug and release). • Check for user-disabled features. • Tailor image resolution to device; use thumbnails. • Launchers instead of full controls. • Disable page transitions. • Use virtualized lists, load on demand. • Test on all your target emulators; focus on the LCD. • Test on real devices. • Use the profiler (Store Test Kit). • Use developer.nokia.com remote device access. • Seek out memory spikes.

16. Out-of-memory conditions • Native allocation failures. • Managed OutOfMemoryExceptions. • Managed framework low-memory conditions and GC. • Failures outside your control.

17. Demo: memory metrics

18. Memory metrics – sample run

19. Memory metrics APIs

20. Memory cap options • Foreground app only. • MAX_CAP == red line on your car rev-counter.

21. Memory cap options

22. Screen resolution and scaling

23. Multi-res

24. Demo: test image scaling

25. Image scaling

26. Summary • For maximum success, do work to support the widest range of devices. • Your app belongs to a balanced ecosystem. • Profile your app, query the device, monitor dynamic features and memory.

27. Resources • App memory limits for Windows Phone 8: http://aka.ms/Tfdyf7 • Developing apps for lower-memory phones: http://aka.ms/To4as5 • The evolution of Windows Phone memory management: http://aka.ms/Jo85ot • Best practice tips for delivering apps with 256 MB: http://aka.ms/Inx8pg • Optimizing apps for lower-cost devices: http://aka.ms/Rwt4ll • App platform compatibility for Windows Phone: http://aka.ms/Y8fxim • Windows Phone 8 Development Internals (book): http://aka.ms/J83ips

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