c# - Does threadpool get shared between application domains?

Question

Consider a process which is creating multiple application domains. Do these Application domains share same thread pool? If yes, how is it coordinated between multiple application domains?

Answer 1

The ThreadPool is shared across all appdomains - since that means threads might end up switching between appdomains (potentially often!) there's been perf work around that:

http://blogs.msdn.com/b/ericeil/archive/2009/04/23/clr-4-0-threadpool-improvements-part-1.aspx

[...] In fact, we violate this “rule” already: since .NET 3.5, the CLR thread pool has maintained separate FIFO queues for each AppDomain in the process, and an additional independent FIFO queue for “native” work items such as those queued by a host (ASP.net being the prime user of this feature). We round-robin between these work queues, allowing each to execute work for some time before moving on to the next.[...]

BTW, note that strictly speaking the ThreadPool isn't shared across the entire process anymore, since the v4 CLR allows loading side-by-side with V2, and each will have its own threadpool.