.NET Garbage Collector - what is its thread priority?

Question

I have found some great articles (Maoni, Richter #1, Richter #2) giving many details as to the theory and practice of the GC, yet I cannot find anything that states how the

Answer 1

the garbage collector runs at lower priority than critical threads

Answer 2

The thread that the GC runs on depends on which version of the GC your app is using.

The answer to this question is contained in a blog post I've written: How to determine which garbage collector is running

Answer 3

In CLR via C#, Richter explains that:

A special high-priority CLR thread is dedicated to calling Finalize methods

(see the "Finalization Internals" heading of chapter 20)

This is the only context in which he talks about a garbage collector thread. A little earlier in the chapter, he explains that garbage collection is started in response to one of the following events:

• Generation 0 is full
• Call to GC.Collect
• Windows is reporting low memory conditions
• The CLR is unloading an AppDomain
• The CLR is shutting down

...which suggests that the only thread created by the garbage collector is this single, "high-priority" finalizer thread.

Edit: He then goes on, in "Concurrent Collection", to explain that:

On a multiprocessor system running the workstation version of the execution engine, the garbage collector has an additional background thread to collect objects concurrently while the application runs. [...] The garbage collector has a normal priority background thread that marks unreachable objects.

Answer 4

The GC thread priority is an implementation detail, right now they are running in normal priority, however the finalizer thread is running as a high priority and has a timeout as well.

Answer 5

The GC thread runs at a normal priority. The finalizer thread runs at "Highest" priority.

You can see this by turning on the Debug "Thread" window, and breaking anywhere in a managed application. The threads are all listed (although they're not named), with their priorities. It takes a bit to decipher which is which, but there will be an extra "Normal" and "Highest" priority thread, which correspond to the GC and the Finalizer thread.