MSDN Magazine - March 2008 - (Page 18)

course, whether or not this approach should be taken can only be determined after measuring performance of cold startup with and without generated native images because the actual benefit of NGen on cold startup depends on the application code and size, so it is not guaranteed to give a significant startup improvement even if there is no JIT involved at startup time. One way to determine if and when JITing is happening is to use the Managed Debugging Assistant (MDA). JIT MDA allows you to either break into the debugger or print debug information when a method is being JITed. The MDA can be enabled by setting an environment variable, as follows: COMPLUS_MDA=JitCompilationStart In general, in order to ensure that NGen is going to benefit cold startup performance, make sure that: • The entire application is NGen-ed. • There is no rebasing. Rebasing is a very expensive operation, and rebased code cannot be shared. You can find more details on how to set the base address at msdn.microsoft.com/msdnmag/issues/06/05/CLRInsideOut. • Assemblies are installed in the Global Assembly Cache (GAC). Strong name verification requires touching the entire file, but strong name verification is skipped for all assemblies installed in the GAC. The application will break into the debugger when code is being JITed. The MDA can also be set using the registry or the application’s .config file. See the “Startup Performance Resources” sidebar for more details on how to use MDA. Authenticode Verification Startup Performance Resources The following previously published CLR Inside Out columns all contain valuable information for further investigation: Improving Application Startup Time by Claudio Caldato msdn.microsoft.com/msdnmag/issues/06/02/CLRInsideOut Includes some useful tips on how to write code in such a way that it has less impact on the application startup. The Performance Benefits of NGen by Surupa Biswas msdn.microsoft.com/msdnmag/issues/06/05/CLRInsideOut Provides a good overview of the NGen technology with a focus on performance. This article is useful for understanding the costs and benefits of using NGen when considering different scenarios such as warm startup, code sharing, cold startup, and so on. Investigating Memory Issues by Claudio Caldato and Maoni Stephens msdn.microsoft.com/msdnmag/issues/06/11/CLRInsideOut This piece is not related to startup per se, although it discusses working set, which is another important performance metric. The article covers some more advanced techniques that can be used to determine why a managed application is using too much memory. Also, you might want to check out the following articles that provide further information to help you reduce startup time: Bug Bash: Let the CLR Find Bugs for You with Managed Debugging Assistants by Stephen Toub msdn.microsoft.com/msdnmag/issues/06/05/BugBash Talks about MDAs, which are debugging aids that work with the CLR to provide information on the state of the runtime. They provide information about runtime events that you would ordinarily not be able to generate. Inside the Windows Vista Kernel by Mark Russinovich microsoft.com/technet/technetmag/issues/2007/03/VistaKernel Explains how SuperFetch operates and how ReadyBoost adds to RAM via USB without adding RAM. Signing and Checking Code with Authenticode msdn2.microsoft.com/ms537364 Gives you all the information you need to understand the Authenticode signing process. Runtime Profiling msdn2.microsoft.com/w4bz2147 Explains how to use PerMon and what the different counters mean. Assemblies can be authenticode-signed using the signcode tool. Authenticode verification always has a negative impact on startup because authenticode-signed assemblies need to be verified by a Certificate Authority (CA). The verification requires validating the CA used to sign the assemblies, which is a very expensive operation that requires network access (if the CA is not installed locally on the same machine). Ideally, you want to avoid authenticode-signing of your assemblies and use strong name signatures instead. If authenticode-signing cannot be avoided, the verification can be skipped in the .NET Framework 3.5 by using the following configuration option: Note, however, that even when authenticode-signing is necessary, most of the time required for the authentication can still be saved simply by installing the CA certificate on the client machine. Wrapping Up In order to achieve good cold startup performance, the best thing to do is to keep the code that is executed at startup time very lean. This means postponing initialization that is not strictly needed, checking all the references to make sure they are not loaded too soon and trying to use classes and methods that don’t require a lot of code to be loaded. Remember, the goal is to reduce disk access. This is not an easy task, but Xperf, a new, useful tool included in the upcoming Windows Server® 2008 SDK uses Event Tracing for Windows (ETW) to track loaded modules, context switches, and other events to help determine what happens during application startup. With XPerf it will be possible to collect very precise metrics on application startup time. The “Startup Performance Resources” sidebar contains many more references that you’ll find helpful. Send your questions and comments to clrinout@microsoft.com. Claudio Caldato is a Program Manager for Performance and Garbage Collector on the CLR team at Microsoft. 18 msdnmagazine CLR Inside Out http://msdn.microsoft.com/msdnmag/issues/06/05/CLRInsideOut http://msdn.microsoft.com/msdnmag/issues/06/05/CLRInsideOut http://msdn.microsoft.com/msdnmag/issues/06/02/CLRInsideOut http://msdn.microsoft.com/msdnmag/issues/06/05/CLRInsideOut http://msdn.microsoft.com/msdnmag/issues/06/11/CLRInsideOut http://msdn.microsoft.com/msdnmag/issues/06/05/BugBash http://microsoft.com/technet/technetmag/issues/2007/03/VistaKernel http://msdn2.microsoft.com/ms537364 http://msdn2.microsoft.com/w4bz2147

Table of Contents Feed for the Digital Edition of MSDN Magazine - March 2008

MSDN Magazine - March 2008 Contents Toolbox CLR Inside Out Data Points Advanced Basics Office Space Introducing ASP.NET MVC Loosen Up CI Server Performance Office Development Test Run Security Briefs Extreme ASP.NET Foundations .NET Matters {End Bracket}

MSDN Magazine - March 2008

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