Fixing Image Performance for The Worst iPhone
summary
Rebuild of a feed that fetches ~200 high‑res images per page to run on an iPhone 6S Plus (2 GB RAM) shows why naive URLSession prefetching and synchronous URLCache hits choke CPU and memory: 10 projects took ~18.6s and caused OOM. Solution: keep an in‑memory resized cache, fetch+resize off the network thread, limit workers with NSOperationQueue maxConcurrentOperationCount = 3, store a 25% preview and overlay full res when ready. Result: smooth scrolling, avoided OOM, and near‑60 FPS on the worst phone.
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chapters (11)
- 0:00Intro
- 1:03The problem
- 2:12Context
- 5:02Run Loop Main Thread
- 8:40Prefetch
- 16:53Resize
- 20:00Thread Problems
- 23:17Memory Problems
- 26:32Cache Issues
- 30:30Why it works
- 31:51What didnt work
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