Александр Терещук - memory analyzer tool and memory optimization tips in android

MEMORY ANALYZER TOOL AND MEMORY OPTIMIZATION TIPS IN ANDROID

Olexandr Tereshchuk

Memory efficiency

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.

Zygote

Zygote – closer look

DEX

DEX – closer look

Garbage Collection: Mark and Sweep

Garbage Collection: Concurrent Mark and Sweep

initial mark — stop-the-world.

mark — Concurrent.

preclean — Concurrent.

remark — Stop-the-world.

sweep — Concurrent.

Garbage Collection: Concurrent Mark and Sweep

Eclipse Memory Analyzer Tool

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

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

Demo

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”

Immediate Dominator

Immediate Dominator

Immediate Dominator

Immediate Dominator

Immediate Dominator

Demo

Common pitfalls

“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);

}

Non-static Handler class

public class MyActivity extends Activity {

Handler myhandler = new Handler() { ... };

}

WebView (only for 2.x)

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]; }

}

Questions ?

The End

Email: atereshchuk@stanfy.com.ua

Skype: rivne2