Performance tracing a Windows Store application with dotTrace
More and more developers are jumping on the opportunity to create applications for the Windows Store. Since most of these apps are very visual and need to be very responsive, it’s really important to know if and where there’s room for improving the application’s code. With the release of dotTrace Performance 5.3, you can now profile Windows Store applications and test projects from within Visual Studio.
As a sample project, I’ve created a simple RSS feed viewer which displays all blog posts on the JetBrains .NET blog. In the screenshot below, you’ll see that there’s a list of blog posts on the left and their contents on the right.
When using the application, everything feels smooth and responsive. Nevertheless it’s good practice to use a profiler to check if you have any potential bottlenecks. After installing the latest version of dotTrace Performance, you will find a new menu item in Visual Studio 2012 from which you can launch a profiling session.
From this menu, you can either profile the current startup project that’s open in Visual Studio, or launch a profiling session for another application. Let’s go with Profile Startup Project as you will probably have it open in your IDE.
Before the profiling session starts, you have to specify how you want to profile. Specifics on all the knobs and handles can be found in the dotTrace Web Help section. For this profiling session, I’ve selected the line-by-line profiling mode. Typically your first profiling session would be based on sampling (less precise but faster) and once you know what you are after you can have more precise results by selecting the tracing or line-by-line profiling mode. Since my RSS reader is a fairly small and simple application, I’m immediately opting for the most precise results using line-by-line mode.
After clicking Run, your application will be launched. If you’re not sure what you’re looking for, simply navigate through it and use it. I’ve clicked a couple of blog posts and waited for them to show up in the application. Once you feel you’ve collected enough information, click the Get Snapshot button in the dotTrace profiler window.
A snapshot of your profiling session is now shown. On the left hand side, you can select one of the various views available in dotTrace Performance to dive into the collected results. In the next screenshot, I’ve selected the Threads Tree. You will notice that the first two threads shown are annotated with a red arrow instead of a black one. This is because those threads have been using the CPU much more than the other threads.
It may be worth investigating the Main Thread, but most often the time shown here is the total time you have had your application running. Thread #3 in the current profiler snapshot is more interesting. It seems that by clicking just a couple of posts in the application, there’s 1430ms spent in the ItemListView_SelectionChanged method. If I drill down deeper, it looks like the TrackView method is taking 1418ms out of that time. That’s a large percentage of time!
If you look at the source code in dotTrace’s bottom pane, the purpose of this TrackView() method is to gain some insight into which posts are being read through the RSS feed viewer application. This method is obviously taking quite some time and may slow down the displaying of a post when I’m using the application on a slower Internet connection.
By profiling this RSS feed viewer Windows Store application, I’ve now successfully identified a potential performance issue even if there was no direct reason for me to go and dive in. Go and download a trail version of dotTrace Performance and profile your own applications too. It may make them much more responsive once published to the Windows Store.
Enjoy profiling your Windows Store applications!
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