Asynchronicity in D

[dsimcha]

== Quote from Sean Kelly (sean at invisibleduck.org)'s article
> On Mar 31, 2011, at 11:48 AM, dsimcha wrote:
> > == Quote from Andrej Mitrovic (andrej.mitrovich at gmail.com)'s
> article
> >> Are fibers really better/faster than threads? I've heard rumors that
> >> they perform exactly the same, and that there's no benefit of using
> >> fibers over threads. Is that true?
> >
> > Here are some key differences between fibers (as currently implemented
> in
> > core.thread; I have no idea how this applies to the general case in
> other
> > languages) and threads:
> >
> > 1.  Fibers can't be used to implement parallelism.  If you have N > 1
> fibers
> > running on one hardware thread, your code will only use a single core.
> It bears mentioning that this has interesting implications for the
> default thread-local storage of statics.  All fibers running on a thread
> will currently share the thread's static data.  This could be worked
> around by doing TLS manually at the fiber level, but it's a non-trivial
> change.

Let's assume for the sake of argument that we are otherwise ready to make said
change.  What would the performance implications of this be for programs using TLS
heavily but not using fibers?  My gut feeling is that, if this has considerable
performance implications for non-fiber-using programs, it should be left alone
long-term, or fiber-local storage should be added as a separate entity.