APP STARTUP TIME WINDOWS 8
While this profile technique works like a charm on Windows 8 desktop, I’ve yet to notice any difference in the startup time of apps on Windows RT.
APP STARTUP TIME CODE
Yet, this technique is not the panacea, because it still requires the CPU to JIT code every time, preventing the rest of the app to use that CPU-time for some other useful tasks. In later startups of the app, that file is used of JIT code ahead of time, substantially improving the app’s startup time. Pre-JIT is based on profiling how an app JITs code, then creating a file out of it that can be bundled with the final app package. The good news is that there are workaround for this slow startup, Pre-JIT and NGEN. The drawback of this approach is that managed code apps do have an extremely poor first launch experience, where the JIT kicks in every time. Microsoft chose not to JIT metro apps on installation supposedly to improve the user's interaction flow with apps, and did not choose to make it in the cloud like the Windows Phone team did, starting from Windows Phone 8. This JIT phase is expected though, and is since. This time is actually spent in the JIT, where big methods tend to take more time to be JITed, sometimes on the UI thread, making the app sluggish. Profiling such an app that starts slowly is very interesting, when looking a the Visual Studio profiler, where during these 17 seconds, about a third is spent in a “clr.dll” module in exclusive time (time spent only in this module and not its descendants). Having an app that is useable after 16 to 18 seconds is definitely not acceptable, let alone the fact that the Splash Screen can disappear after 6 to 8 seconds. Running apps on the Surface can be troubling. Profiling a slow starting app on a Surface RT Now that the Surface RT devices are available, we’re facing quite a few challenges in terms of code execution performance, and I’m going to discuss a few tips and tricks about the Managed Code JIT on Windows RT. Back then, I was only able to work on x86/圆4 architectures, as ARM/Windows RT devices were not available. There is also a way to check for these native images to act accordingly.Ī while back, I’ve had the chance to work with the guys that are behind the Pre-JIT feature of the CLR 4.5 for Metro Apps.
TL DR: The JIT can take over a third of the startup time of a managed Metro App, and using Native Image Generation (NGEN) can greatly improve the startup time of these apps.
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