Delphi COM EXE and Threading

Question

Just want to confirm with the COM/DCOM experts out there...

I have a Delphi COM EXE that is running on a server (threading is Single Apartment) and another copy of that same EXE starts up on the same server (a server that has say 2 processors with dual core so the task manager shows 4 separate graphs) will they take turns waiting for each other or will they run on separate cores?

I found a post somewhere that said

"If two clients need to use the same object, they have to take turns. With this threading model the instance data is safe, global data must be protected using critical sections or some other form of serialization. Of course, the thread's local variables are reliable across multiple calls."

Answer 1

You've missed the "different objects from the same server" part from the same paragraph. Since you have "Single instancing" you get a separate server for each COM object instance, so calls to those instances can be processed in parallel and COM will not have to provide any mutual exclusion.

Think of it this way. Threading models are there to provide thread safety - synchronized access to data shared between threads of the same process. You have one object per process, so there's no two threads will try to access the same object unless of course you try to pass a pointer to one object into another object method call.