KnownTypeProvider causing performance problem in large application

[David Martines]

Our app has over 600 request/response pairs (and we've still many features to implement).  A performance degradation is noticed (over 100ms extra to each wcf call) when this many types are registered.  I imagine something in WCF is looping over this list on each call.   As a workaround, we clear the KnownTypeProvider on app startup after registering request/response assemblies.  We've overriden the RequestDispatcher to dynamically register the request and response types as needed, and then clear again on disposal.  This works well, but we've discovered a threading bug, since one thread may have cleared a type from the KnownTypeProvider that another thread still needs.  Any ideas on how to do this properly?