I'm using OpenGL ES 1.1 and CADisplayLink to animate a 3d scene. If the iOS device has been rebooted fairly recently, the animation is smooth and the time delta between two displayLink.timestamp calls is fairly even. But after a few hours or days of the iOS device being used and my app is sometimes run a few times, the animation becomes jerky and the time deltas ramp up and then reset to a lower value only to ramp up again.

Like this:

2012-09-01 23:42:58.770 [2678:707] dt= 0.021139

2012-09-01 23:42:58.787 [2678:707] dt= 0.022183

2012-09-01 23:42:58.804 [2678:707] dt= 0.023223

2012-09-01 23:42:58.820 [2678:707] dt= 0.024270

2012-09-01 23:42:58.837 [2678:707] dt= 0.009679

2012-09-01 23:42:58.853 [2678:707] dt= 0.010750

2012-09-01 23:42:58.870 [2678:707] dt= 0.011766

2012-09-01 23:42:58.887 [2678:707] dt= 0.012806

2012-09-01 23:42:58.903 [2678:707] dt= 0.013847

2012-09-01 23:42:58.920 [2678:707] dt= 0.014890

2012-09-01 23:42:58.937 [2678:707] dt= 0.015933

2012-09-01 23:42:58.953 [2678:707] dt= 0.016976

2012-09-01 23:42:58.970 [2678:707] dt= 0.018011

2012-09-01 23:42:58.987 [2678:707] dt= 0.019055

2012-09-01 23:42:59.003 [2678:707] dt= 0.020097

2012-09-01 23:42:59.020 [2678:707] dt= 0.021143

2012-09-01 23:42:59.037 [2678:707] dt= 0.022181

2012-09-01 23:42:59.054 [2678:707] dt= 0.023222

2012-09-01 23:42:59.071 [2678:707] dt= 0.024288

2012-09-01 23:42:59.087 [2678:707] dt= 0.009624

2012-09-01 23:42:59.103 [2678:707] dt= 0.010728

2012-09-01 23:42:59.121 [2678:707] dt= 0.011763

2012-09-01 23:42:59.137 [2678:707] dt= 0.012808

2012-09-01 23:42:59.153 [2678:707] dt= 0.013847

2012-09-01 23:42:59.170 [2678:707] dt= 0.014891

2012-09-01 23:42:59.187 [2678:707] dt= 0.016002

2012-09-01 23:42:59.203 [2678:707] dt= 0.016979

2012-09-01 23:42:59.220 [2678:707] dt= 0.018016

2012-09-01 23:42:59.237 [2678:707] dt= 0.019042

2012-09-01 23:42:59.253 [2678:707] dt= 0.020099

2012-09-01 23:42:59.270 [2678:707] dt= 0.021138

2012-09-01 23:42:59.287 [2678:707] dt= 0.022185

2012-09-01 23:42:59.304 [2678:707] dt= 0.023222

2012-09-01 23:42:59.320 [2678:707] dt= 0.024265

2012-09-01 23:42:59.337 [2678:707] dt= 0.009681

2012-09-01 23:42:59.354 [2678:707] dt= 0.010736

And then if the iOS device is rebooted the animation is smooth again.

The problem even occurs on my menu screen when almost no game related calculations are going on in the UpdateAnimation() function.

I don't understand what is going on and why a fresh reboot will always fix this problem for a while.