Sunday, October 21, 2012

Multicore JIT can jump start your app launch (with two lines of code and without requiring you NGen)

Over the last ten years of building the .NET runtime, quite a number of assumptions have changed. Early on we could assume that most computer users only had one processor. Today, the assumption is that you have at least two processors. While including parallelism in an app for performance challenges most developers, what if that parallelism came for free? That's exactly what we've done with our newest CLR performance feature. Today, Dan Taylor, a program manager from the CLR performance team, shares how multicore JIT can make your app start faster. The best part -- you just have to include two lines of code to try it out. Super easy! --Brandon

In this post, I will provide an in-depth review of how the Multicore JIT technology works, and then show you how easy it is to use in your .NET Framework 4.5 apps.

App launch is faster with Multicore JIT

On the .NET Framework performance team, we spend a lot of time looking at the launch performance of managed applications. Large managed applications require JIT (just-in-time) compilation at launch time, so improving launch performance can be challenging. .NET Framework developers have been able to use Ngen.exe (Native Image Generator) to move code generation from application startup time to installation time. However, for the most part, this pre-compilation option is available only for large .NET Framework applications that also happen to have an installer.

As developers continue to take advantage of the great productivity benefits of the .NET Framework, they are using managed code in places where there is no installer and where Ngen is not available. To address the needs of these developers and to round out our portfolio of performance technologies in the .NET Framework 4.5, we have introduced Multicore JIT, which uses parallelization to reduce the JIT compilation time during application startup.

With Multicore JIT, methods are compiled on two cores in parallel. The more code you execute on your startup path, the more effective Multicore JIT will be at reducing startup time. Improvements of 20%-50% are very typical, which is great news to anyone developing medium to large .NET Framework applications that are not able to take advantage of NGen. You can improve the startup time of your application by up to 50% with very little work, even if it runs off of a USB stick.

Real-world benefit of Multicore JIT

Let’s take a look at how this works in practice with a few real-world applications. recently moved to Windows Server 2012 and the .NET Framework 4.5. Because of Multicore JIT, their ASP.NET based services now start up 50% faster, going from an average of around 155 seconds to just under 80 seconds. You can read more about the results with Multicore JIT in their recent blog post.

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