Simon, Thank you for explanation.
- We have an accurate GC, which means that the Haskell stack can be movable, whereas the C stack isn't. So we can start with small stacks and enlarge them as necessary.
What is the difference between the Haskell stack and the C stack? I guess that the C stack means CPU's stack. Is the Haskell stack a virtual stack for a virtual machine (STG machine or something)? I quickly read several papers but I have no idea.
- We only preempt threads at safe points. This means that the context we have to save at a context switch is platform-independent and typically much smaller than the entire CPU context. Safe points are currently on allocation, which is frequent enough in GHC for this to be indistinguishable (most of the time) from true preemption.
I seems to me that StgRun saves CPU registers. You mean that StgRun depends on CPU a bit but the rest part of context is CPU independent? --Kazu