I have created a project on GitHub so I can learn how to optimize networking for my iOS apps. I have used blocks and GCD heavily and after watching WWDC 2012 videos and videos from past years I learned that I may be able to do more with NSOperationQueue. Specifically I can control the number of concurrent operations (network connections) as well as provide cancellation of operations. I am experimenting with allowing 1, 2, 4, 8 and 16 concurrent operations and I am seeing interesting results that I did not totally expect. I am measuring the results but I wonder if there is more that I should be measuring.
You can find sample project here:
https://github.com/brennanMKE/OptimizedNetworking
Since I am using the async API of NSURLConnection there is plenty of benefit to having many concurrent connections because the API spends a fair amount of time waiting for HTTP packets. Previously my code would start with an array of items to download and request them all sequentially, which is prevents the benefits of concurrency. I have also been using notifications to cancel network connections. Now I can do that with this project through operations and I have set them up to use a value for priority and a category so that I can prioritize and sort downloads and cancel a category of operations. I may choose to use a category for each view and when a user leaves a view all operations for that view will be cancelled using the category. This will free up resources for the active view.
One concern with using more concurrent operations is CPU usage as well as I/O, but I am not aware of a way to measure these values with iOS. The equivalent of the "w" command in iOS to show CPU usage could be useful. I am less concerned about I/O but measuring it would be more comprehensive.
My main issue with how I was doing networking was a responsive UI. I found that what I have