What’s new for Performance in Silverlight 4 GDR1

Hopefully folks saw the announcement about Silverlight 4 Service Release GDR1 availability. See Tim’s link here and KB2164913.  The service release is being distributed by Microsoft Update as an Important update on Vista/Win7 and Critical update on Windows XP/ Windows 2003 Server. Mac and other Windows users who did opt-in for Microsoft Update will be prompted to install Silverlight 4 GDR1 soon after 9/1/2010.


In addition to other fixes (See above posts), this release fixes some key performance issues which I wanted to highlight:

  1. Fixed various memory leaks including:
    1. Leak when mouse capture is used (ScrollViewer, Button, Slider etc.)
      e.g.  when you use CaptureMouse() for drag and drop scenarios.
      (See some discussions
    2. Leak where UserControl cannot be garbage-collected when it contains inline data template. 
      (See some discussions here)
    3. Other memory leaks in some other corner scenarios.
  2. Application cold startup improvement:
    1. Avoid loading of both IL and NGEN’d images.
    2. Allow the Silverlight pre-fetcher (agcp.exe) to run during the Silverlight detection script so that once an application redirects, the Silverlight pages are read from disk.  (*The actual startup improvement depends on the application download size and network speed)
  3. Fixed animation jitter caused by the Silverlight pre-fetcher (agcp.exe) shutting down 10 seconds after a Silverlight application is launched. This was typically seen on a single core machine.

 Enjoy. Jossef.

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