Making good use of XCode performace tools

What are the best practices, tricks, and tutorials for using XCode's performance tool开发者_高级运维s, such as the Leak Monitor and the CPU sampler, for someone trying to debug and enhance performance of an iPhone application? Thanks!

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It depends entirely on the application and on what you are trying to do. Are you trying to optimize the whole application or are you focused on a particular problem area? Are you trying to reduce memory usage, reduce CPU usage, and/or make the app more responsive?

Before you start the performance analysis, use the static analyzer to analyze your code. It will often find memory management problems that would lead to leaks that would cause your app to potentially crash on the device.

Once all of the analyzer identified problems have been fixed, the best approach is to start by identifying perceived performance problems. That is, focus on performance problems that the user would notice. Then analyze those. If you can get away with it, do the analysis on the app running in the simulator as the turnaround time is faster.

If the problem is one of bloat, use Object Alloc and Leaks to figure out why.

If it is one of laggy/sluggish behavior, use the CPU tools to figure out where the cycles are going. Keep in mind, though, that sluggish behavior may not be because of CPU usage, but may be because the main event loop is blocked by something, most likely incorrect concurrency patterns. In that case, you'll see all samples on the main thread in some kind of a lock or wait function.

Beyond that, you'll need to identify specific scenarios to yield specific answers.

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use instruments in that use object allocation activity monitor, leaks memoer monitor

and test your app