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I am using CADisplayLink to perform a function called gameLoop at 60 FPS and at first the application runs perfectly. Then at a random time (could be 5 seconds or 1 minute the fps drops to around 40 FPS.

After days of searching forums, debugging, optimizing my rendering, profiling, and analyzing my app, I decided to remove everything from the gameLoop function except for a few lines which calculate how long it has been since the last call to gameLoop. I cannot figure out why CADisplayLink calls gameLoop at 60 FPS for a while then calls it at 40 FPS thereafter when gameLoop does almost nothing.

I implemented a pause/unpause function which invalidates the display link and restarts it. When I restart the display link, the app runs at 60 FPS again until it drops randomly.

Thanks in advance to anyone who can give me some insight as to why this is happening.

Benoit
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user1591589
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2 Answers2

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I decided to try OpenGL ES 2.0 and the GLKit API to see if that would fix the issue. After reading the apple docs and some tutorials I ported the code and tested it with the Xcode analyzer and the Performance Detective. The GLKViewController's Update and drawInRect functions get called at 60 FPS and everything runs perfectly.

user1591589
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If you're on iOS 5 make sure to set your view's opaque paramater to YES. I'm guessing something with compositing the screen with other CoreAnimation layers is causing the slow down. And I'm guessing the GLKIT API does this in it's setup.

http://www.cocos2d-iphone.org/forums/topic/app-often-but-not-always-runs-at-40-fps-at-startup-rather-than-60-fps/

insomniac2846
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