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Of all the Instruments Trace Templates, I love using:
EXEC_BAD_ACCESS errors.UITableView scrolling.I always hear people saying to profile my app's memory usage & performance.
I've used Allocations and see that my iPhone app starts at 1 MB total allocated memory and grows to 5 MB after normal usage. What is too high amount of memory usage on the iPhone? iPad? Mac?
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Press Ctrl + Shift + Esc to launch Task Manager. Or, right-click the Taskbar and select Task Manager. Select the Performance tab and click Memory in the left panel. The Memory window lets you see your current RAM usage, check RAM speed, and view other memory hardware specifications.
The easiest way to profile a single method or function is the open source memory-profiler package. It's similar to line_profiler , which I've written about before . You can use it by putting the @profile decorator around any function or method and running python -m memory_profiler myscript.
Memory profiling enables you to understand the memory allocation and garbage collection behavior of your applications over time. It helps you identify method calls in the context within which most memory was allocated and combine this information with the number of allocated objects.
To answer the whys, profiling memory usage is especially important for iOS apps because iPhones and iPads have much less RAM than Macs. The iPhone 4 has 512 MB of RAM, but earlier versions had 256 or 128 MB. Factor in the RAM the OS uses and multitasking, and your app doesn't have much RAM to waste so it's important to be aware of how much memory your app uses.
Profiling performance is something you usually do when your app is running slowly. Profile it to find the slow spots in your code so you can make the code run faster. If your app runs fine, you don't have much need to profile for performance.
To answer the hows, use the Allocations instrument to measure memory usage. The Live Bytes column in the All Allocations category tells you the amount of memory your app is currently using. The Allocations instrument's heapshot analysis measures memory growth in your app. Use the menu on the left side of the jump bar to do heapshot analysis.
The Time Profiler instrument profiles your app for performance. The difficult part of using the Time Profiler instrument is interpreting the results. The Time Profiler instrument isn't going to tell you your app spends 75% of its time in Function X. You have to dig through the data to find the slow spots in your code.
Regarding acceptable memory usage, it depends on the devices you want to support and the app. An app like Xcode using 100 MB of RAM would be OK, but an app like TextEdit using 100 MB for a one page document would be a problem. 5 MB shouldn't be a problem for an iOS app.
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To address some of the comments in Mark's answer:
Allocations live bytes doesn't include OpenGL texture memory, which is used by CALayer/UIViews. This is the source of the disagreement with the Memory Monitor.
See the answer to this question here: Understanding the memory consumption on iPhone
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