Why Is mscorsvw.exe Running?

Martin Brinkmann
Jul 26, 2008

My system felt a bit sluggish after starting the installation of a new application and a quick check of the task manager revealed a process named mscorsvw.exe that was running on my system using nearly 40% of my CPU. I never heard about that file before and a quick check on the Internet revealed that it was related to the Microsoft .net Framework.

I never experienced the behavior on my old computer though and it seemed as if the process would not go away on its own. It was there, eating my CPU cycles even after quitting the program installation.

Apparently mscorsvw.exe is precompiling .NET assemblies in the background which can take anywhere from 5 to 10 minutes and then some more for low priority assemblies. So the easiest way to get through it is by sitting it out.

If you want to get rid of it completely immediately you could issue the command ngen.exe executequeueditems. Ngen.exe is located in the Microsoft .net Framework directory in the Windows dir.


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  1. Rich Lander [MSFT[ said on August 8, 2013 at 9:00 pm

    We wrote a blog post on this topic. It also includes a script that you can run.


  2. under a rock said on October 18, 2009 at 3:28 am

    best thing to do is to go into services and switch .net runtime optimizer to manual. this will prevent it from “popping up” unexpected.

    1. Michelle said on September 15, 2011 at 10:27 pm

      Thanks for your help here…..much more helpful than everything I searched on internet

    2. G said on October 22, 2009 at 3:21 pm

      Thanks for tip, the process just froze my system a few times.

  3. Rarst said on July 26, 2008 at 5:18 pm

    Yep, had similar experience recently. Tiny setup file unpacked some stuff and started really long process of compiling.

    Hadn’t exactly improved my opinion on framework based apps. :)

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