[dmd-concurrency] Smoke test

[Robert Jacques]

On Thu, 07 Jan 2010 20:28:23 -0500, Walter Bright <walter at digitalmars.com>  
wrote:
> Having a per-thread gc is an optimization, not a fundamental feature of  
> the concurrency model. For one thing, it precludes casting data to  
> immutable. For another, it may result in excessive memory consumption as  
> one thread may have a lot of unused data in its pool that is not  
> available for allocation by another thread.
> _______________________________________________
> dmd-concurrency mailing list
> dmd-concurrency at puremagic.com
> http://lists.puremagic.com/mailman/listinfo/dmd-concurrency

I would disagree; it's completely possible to allow safe casting to  
immutable/shared with thread-local GCs. It just requires language support.  
For example, adding a GC function which is called whenever a shared cast  
occurs. In the current GC, the function does nothing and everything  
proceeds as normal. With thread local GC, however, this function would  
publish the casted object to a list. The local GC could then pin all  
objects on the list and the shared GC could mark/sweep the list entries  
instead of the objects themselves.

Also, today a thread-local mark-sweep GC equals a modern concurrent shared  
GC (according to Apple). So going forward, I think thread local GCs will  
be a big thing.