This document discusses Eclipse Memory Analyzer (MAT), a tool for analyzing memory usage in Android applications. It begins with an overview of MAT and why memory analysis is important for identifying leaks and reducing memory footprint in apps. Key MAT features are demonstrated, including viewing dominator trees, inspecting object fields and collections, class histograms, and grouping by value. The document also covers generating heap dumps from Android devices and investigating object retention paths to find leaks.

1. Eclipse Memory Analyzer
Tool
Lakshman Kakkirala
little eye labs

2. Agenda
● Memory Analysis
● Some Definitions
● An example leak code
● Demo of MAT and some basic functionality

3. Prereqs
● Android app development
● Basic Heap and Garbage Collection
Disqualification
● Advanced knowledge of MAT :-)

4. littleEye appInsight
CT Scanner for your app
http://www.littleeye.co

5. Why Memory Analysis?
● Identify Leaks
● Reduce memory footprint

6. Typical problems
● Holding Context object (an Activity, a View
or a Drawable)
which actually happens to be an Activity
● Non-static inner classes
● Caches
● Aggressive Caching

7. Some definitions
● Shallow Size
● Retained Size
● Dominator
● Dominator Tree
● GCRoots

8. Example - Object Graph
E
B 100
100 100
300
A F
100 100
C 100
600
100
200 D
100
100

9. Example (contd) - Dominator Tree
E
B
F
A
C D

10. Example - Memory Leak
public class MainActivity extends Activity {
private static LeakClass leak;
// *NOT A STATIC*
class LeakClass { }
@Override
public void onCreate(Bundle savedInstanceState) {
....
if (leak == null) {
leak = new LeakClass();
}
...
}
}

11. Investigation Tools - LogCat
● D/dalvikvm( 9050 ): GC_CONCURRENT
freed 2049K, 65% free 3571K/9991K,
external 4703K/5261K, paused 2ms+2ms

12. Heapdump
● What - Snapshot of all the objects in the process
○ Fields, References, Primitive Values
○ Classes, Class Loaders
● How to generate
○ DDMS view - "Dump HPROF file" icon
○ android.os.Debug.dumpHprofData(<filename>)
○ signal 10
● Convert to standard HPROF format
○ hprof-convert (only required if using standalone)

13. MAT aka Eclipse Memory Analyzer
Tool
● Standalone - Download
http://www.eclipse.org/mat
● Pros
○ Visible Primitive Data
○ Powerful selection model
○ No setup
● Cons
○ Large dump files
○ Cannot answer code/temporal questions
■ Who/Where/When - an object is created
■ When - an object is garbage collected

14. Demo
Covering
● View Dominator Tree
● Inspector
○ look at the field values
○ browse through entries in a Collection
● Class Histograms
● Group by Value

15. Demo (contd...)
● Immediate Dominators
● Path from GC roots
● Retained Set
● Object Query Language

16. References
● Google IO 2011 - "Memory Management for Android
apps" http://www.google.
com/events/io/2011/sessions/memory-management-for-
android-apps.html
● Java Memory Analysis
http://vimeo.com/21356498
● Markus Kohler's Java Performance Blog
http://kohlerm.blogspot.com
● Memory Analyzer Blog
http://memoryanalyzer.blogspot.in/

18. Backup Slides
Application Attributes:
<application
android:largeHeap="true">

19. Garbage Collection
Pre Gingerbread:
GC: stop the world gc, >100ms
Gingerbread and beyond:
concurrent gc,
two pauses - at the beginning and at the end
< 5ms
partial collections

20. Bitmap
pre-honeycomb:
● pixel data was stored in native mem
● recycle() or finalize()
● invisible to MAT
honeycomb and after:
● pixel data inside dalvik heap
● visible to MAT
● works with partial and concurrent GC

21. Typical Garbage Collections
GC_CONCURRENT
GC_FOR_MALLOC
GC_EXTERNAL_ALLOC (pre-honeycomb)
GC_HPROF_DUMP_HEAP
GC_EXPLICIT - app calling System.gc()