Atomic Ref Counting

[Andrei Alexandrescu]

On 11/21/10 7:59 PM, dsimcha wrote:
[snip]
> Atomic:  258 milliseconds total (258 nanoseconds per iteration)
> Non-atomic:  88 milliseconds  (88 nanoseconds per iteration)
>
> I think this is a small enough overhead that we should just make all reference
> counting atomic.  This would make the race condition pointed out by Michael
> Fortin completely moot IIUC.  It would also make it possible to safely share
> reference counted containers across threads in shared/synchronized wrappers, etc.

Thanks for taking the time to build a credibla baseline. A lot of this 
depends on the perspective. We're looking at a 2.9x slowdown after all.

After discussing this with Walter, our conclusion was that we need to 
solve the problem of calling destructors from a different thread in 
general, not only for reference counting. The fact that you could have 
arbitrary race conditions in destructors definitely is a problem, one 
that needs a solution.

We currently think the solution should be that the GC guarantees 
destructor calls in the same thread as the constructor.


Andrei