2 months ago
- Launch time is a critical metric; even a 1% improvement saves significant time across billions of daily launches.
- Apple claimed a 30% boost in app launch times in iOS 27, achieved through an optimized CPU scheduler and preloading key app data.
- The article explains launch phases: cold launch (process doesn't exist), warm launch (cached data), and no 'hot launch' (just resume).
- Using Instruments, the author measured iOS 26 vs iOS 27: cold launches were 21% faster, warm launches 23% faster, with most gains in pre-main phases.
- Improvements in iOS 27 include faster closure rebuilding (1.5x), fixups (2.5x), and static initializers (3x), while I/O steps remained similar.
- Apple has historically improved launch times (e.g., dyld3, CPU clock warming), but actual gains are often modest, emphasizing the need for developers to optimize their own launch paths.