Unmanaged memory in a .net 4 application pool

Question

I'm trying to track down the source of some unmanaged memory in a .net 4 application

(this is curiosity...I don't have a major problem with it, I just want to know what it is)

My application currently consists of 1 file: index.html - contains "hello world"

From a memory profiler, I load up index.html and it's consuming very little (in fact, the profile hasn't kicked int)

I then load up /fish (which doesn't exist) and now suddenly we're on a total of about 57MB usage, 54MB of which is unmanaged memory.

This seems like a lot of memory for an empty application - and what's in the unmanaged memory

There is an "Unused memory allocated to .NET" of 2.4MB, which I would totally expect.

Curiously, if I switch the app pool to .net 2, the memory doesn't jump in this way

As I said, I'm curious, but I can't find anything about it online.