The document discusses memory analysis and optimization tips for Android applications. It introduces the Eclipse Memory Analyzer tool, which can be used to analyze memory usage and find memory leaks. Some key points covered include the low RAM sizes on Android devices, how the garbage collector works, how to analyze an object's shallow size and retained size, finding memory dominators, and common memory leak pitfalls like non-static handlers and large bitmaps stored in static fields. The document encourages analyzing heap dumps in the Memory Analyzer tool to optimize memory usage and find leaks.

1. MEMORY ANALYZER TOOL
AND MEMORY OPTIMIZATION
TIPS IN ANDROID
Olexandr Tereshchuk

2. Memory efficiency

3. Problem
 Low RAM size – 256MB to 512MB on
most of devices.
 Low CPU performance – harder to
perform full GC.
 Each application works in it’s own
process and VM instance.
 Large system library.

4. Zygote

5. Zygote – closer look

6. DEX

7. DEX – closer look

8. Garbage Collection:
Mark and Sweep

9. Garbage Collection:
Concurrent Mark and Sweep
 initial mark — stop-the-world.
 mark — Concurrent.
 preclean — Concurrent.
 remark — Stop-the-world.
 sweep — Concurrent.

10. Garbage Collection:
Concurrent Mark and Sweep

11. Eclipse Memory Analyzer Tool

12. Shallow size
Shallow size of an object is the amount of memory
allocated to store the object itself, not taking into
account the referenced objects == Sum of the size of
the “object header” and the fields of an object

13. Retained size
 Retained set of X
 The set of objects that would be reclaimed, if we
could delete Object X
 Retained size of X
 The Retained size of an object X is equal to the
shallow size of the „Retained sets“ of X

14. Demo

15. Dominator Tree
 X dominates Y, if all paths from a GC Root
to Y go via X. “X is a Dominator of Y”
 The closest Dominator to Y is called
“immediate Dominator”

16. Immediate Dominator

17. Immediate Dominator

18. Immediate Dominator

19. Immediate Dominator

20. Immediate Dominator

21. Demo

22. Common pitfalls

23. “Static” Drawable
private static Drawable sBackground;
@Override
protected void onCreate(final Bundle state) {
super.onCreate(state);
final TextView label = new TextView(this);
label.setText("Leaks are bad");
if (sBackground == null) {
sBackground = getDrawable(R.drawable.large_bitmap);
}
label.setBackground(sBackground);
setContentView(label);
}

24. Non-static Handler class
public class MyActivity extends Activity {
Handler myhandler = new Handler() { ... };
}

25. WebView (only for 2.x)

26. View.setTag(key,tag) - pre 4.0
public static class MainActivity extends Activity {
private final WeakHashMap<Parent, Parent.Child> mMap = new WeakHashMap<Parent, Parent.Child>();
@Override
public void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// If parents were collected OOM error wouldn't be thrown. But they aren't collected so we get OOM here.
for (int i = 0; i < 1000; ++i) {
final Parent parent = new Parent();
mMap.put( parent, parent.mChild );
}
}
}
public static class Parent {
public final Child mChild = new Child();
public class Child { private final byte[] mJunk = new byte[10*1024*1024]; }
}

27. Questions ?

28. The End
Email: atereshchuk@stanfy.com.ua
Skype: rivne2