Android's Multidex Slows Down App Startup
Article Summary
Michael Ma from Groupon discovered that enabling multidex increased their Android app startup time by 15% on pre-Lollipop devices. Here's how his team clawed that performance back.
When Android apps hit the 65k method limit, multidex is the standard solution. But this convenience comes with a hidden cost: significantly slower app launches on devices running KitKat and below. Groupon's engineering team documented their journey to identify and fix this performance regression.
Key Takeaways
- Multidex caused 15% slower app startup on all Android 4.4 and earlier devices
- Pre-Android 5.0 devices have extra overhead loading classes from secondary dex files
- Using ClassLoader.findLoadedClass() identifies which classes to move into main dex
- Moving startup-critical classes to main dex restored original performance levels
- Treat multidex as last resort after code cleanup and refactoring options
Critical Insight
By identifying and relocating startup-critical classes to the main dex file, Groupon eliminated the 15% performance penalty and matched pre-multidex startup speeds.
