Objective-C
CFTimeInterval startTime = CACurrentMediaTime();
// perform some action
CFTimeInterval elapsedTime = CACurrentMediaTime() - startTime;


Swift
let startTime = CACurrentMediaTime()
// perform some action
let elapsedTime = CACurrentMediaTime() - startTime

Benchmark
extern uint64_t dispatch_benchmark(size_t count, void (^block)(void));
uint64_t t = dispatch_benchmark(iterations, ^{
    @autoreleasepool {
        ...
    }
});
NSLog(@"Avg. Runtime: %llu ns", t);