1. Memory Management for Android Apps Min Ji, Kim Embedded Software Lab. kimmj0857@skku.edu

2. 2/27 Embedded Software Lab. Introduction Google I/O Development Conference, 2011 Google I/O Development Conference ?? Thousands of developers’ festival for two days of deep technical contents. Android, Google Chrome, Google APIs, Google Web Toolkit, App Engine, etc.

3. 3/27 Embedded Software Lab. No more memory management? 512MB RAM2GB RAM

4. 4/27 Embedded Software Lab. Heap Size Heap size limits(for multi-tasking) Nexus One: 32MB Galaxy S: 48MB Nexus 7: 48MB ActivityManager.getMemoryClass() Large Heaps ActivityManager.getLargeMemoryClass() Degrades performance

5. 5/27 Embedded Software Lab. Garbage Collection Heap object reference

6. 6/27 Embedded Software Lab. Garbage Collection Bigger heaps cause longer pauses. Pre-Gingerbread GCGingerbread and beyond Stop-the-worldConcurrent(mostly) Full heap collectionPartial collections Pause times is often over 100ms Pause time is usually less than 5ms

7. 7/27 Embedded Software Lab. Bitmaps Old way(pre-Honeycomb) freed via recycle() or finalizer hard to debug full, stop-the-world GCs New way freed synchronously by GC easier to debug concurrent & partial GCs

8. 8/27 Embedded Software Lab. Overview Changes in Gingerbread and Honeycomb heap size Garbage Collection bitmaps Understanding heap usage Logs Memory leaks Eclipse Memory Analyzer(MAT)

9. 9/27 Embedded Software Lab. Interpreting Log Messages Reason for GC GC_CONCURRENT GC_FOR_MALLOC GC_EXTERNAL_ALLOC GC_HPROF_DUMP_HEAP GC_EXPLICIT

10. 10/27 Embedded Software Lab. Interpreting Log Messages Reason for GC Amount freed

11. 11/27 Embedded Software Lab. Interpreting Log Messages Reason for GC Amount freed Heap statistics

12. 12/27 Embedded Software Lab. Interpreting Log Messages Reason for GC Amount freed Heap statistics External memory statistics

13. 13/27 Embedded Software Lab. Interpreting Log Messages Reason for GC Amount freed Heap statistics External memory statistics Pause time

14. 14/27 Embedded Software Lab. Heap Dumps Binary dump of all objects Create with: DDMS android.os.Debug.dumpHprofData() Convert to standard HPROF format: hprof-conv orig.hprof converted.hprof Analyze with MAT, jhat, etc.

15. 15/27 Embedded Software Lab. Memory Leaks Memory Leak? Referencing to an unused object preventing from garbage collecting

16. 16/27 Embedded Software Lab. Eclipse Memory Analyzer(MAT) Download from http://eclipse.org/mat or Eclipse plug-in is providedhttp://eclipse.org/mat “Shallow heap” and “Retained heap” Shallow heap : just size of object

17. 17/27 Embedded Software Lab. Eclipse Memory Analyzer(MAT) Download from http://eclipse.org/mat or Eclipse plug-in is providedhttp://eclipse.org/mat “Shallow heap” and “Retained heap” Retained heap : total size of memory after freeing that object

18. 18/27 Embedded Software Lab. Eclipse Memory Analyzer(MAT) Dominator Tree Based on graph theory Dominator: closest object on every path to node A B C E D

19. 19/27 Embedded Software Lab. Heap Dumps : Example com.google.android.apps.maps

20. 20/27 Embedded Software Lab. Heap Dumps : Example

21. 21/27 Embedded Software Lab. Heap Dumps : Example

22. 22/27 Embedded Software Lab. Heap Dumps : Example

23. 23/27 Embedded Software Lab. Heap Dumps : Example

24. 24/27 Embedded Software Lab. Heap Dumps : Example

25. 25/27 Embedded Software Lab. Heap Dumps : Example

26. 26/27 Embedded Software Lab. Heap Dumps : Example

27. 27/27 Embedded Software Lab. Heap Dumps : Example