Pauses/computation between function execution?

I'm working on a game and the speed of the game is 60fps, giving me about 16ms to execute what I need to execute. What I'm finding tho is that certain code paths are taking a while to execute. At first I thought this must be an issue with memory allocation/deallocation. It could possibly be, but I have implemented object pooling for the more heavywei开发者_StackOverflow社区ght objects, and this seems to have had little effect.

I have stripped out the offendingly large objects, and replaced them with a much simpler object, yet it still takes about 3ms to make this object. The simple object consists of two custom objects, 2 arrays, and 2 dictionaries. The large object is of an arbitrary complexity. Making the more complex larger objects seem to take linearly more time, taking up to 20-30ms. In many instances in my game I can make a much more complicated object in a fraction of the time. But somehow these specific locations in code cause a serious slowdown.

I am using the following code to profile my functions (from SO originally):

NSDate* methodStart = [NSDate date];
// My code here.
NSDate *methodFinish = [NSDate date];
NSTimeInterval executionTime = [methodFinish timeIntervalSinceDate:methodStart];
NSLog(@"[CH] executionTime to create  %@ = %f", myObject , executionTime );

As best as I can confirm if I do something like the above in an inner and outer function, it looks like there can be a serious slowdown:

Inner function call completed: 4ms

...no code between inner and outer code except timer...

Outer function call completed: 8ms

My current theory is there is 'in-between' computation that occurs between the functions that is causing the serious slowdowns. As I'm new to Obj-C/C I'm not entirely sure what this slowdown could be. It could be threading, it could be because of memory alloc/autorelease/dealloc, or some other kind of unrelated issue. I have attempted to get more info from Instruments with little benefit.

So my question is: Does this sound logical? Is it possible that some kind of computation could be happening between my functions that would take up 2-4ms of cpu on an ipad2? And if my theory isn't possible, any ideas what it could be?

The best way to track down this type of problem is to use Instruments to profile the execution of the code. Often, you can run this against the code on the Mac under the simulator to see where the time is going, however, in this case you may need to profile it on your iPad to be certain.

Remove your NSDate-based profiling code, as NSDate can be a pretty heavy-weight object, especially when you put the results into the autorelease pool, which you are doing here.

If you feel you must do NSDate-based profiling, you should only need to create a single NSDate object and the use: [methodStart timeIntervalSinceNow] to calculate the time delta without having to create a separate object and perform a date subtraction operation.