Linus with some good observations on garbage collection

[Iain Buclaw]

== Quote from Timon Gehr (timon.gehr at gmx.ch)'s article
> Andrei Alexandrescu wrote:
> > I am sorry, you simply have no case - each and every argument you put
> > forth has no strength or is just wrong. We could spend time on debating
> > each, but I suspect that would do little toward convincing you of what
> > is after all a simple fact, but one with many subtle facets. It might
> > not a good use of our time to further engage in a diatribe on this. The
> > delete keyword will go, as will class-specific new and delete.
> >
> >
> > Andrei

Is it correct that the current D GC implementation puts delete'd allocations into
a freelist (or bucket) to be reused when 'new' is invoked again?

> Ok, lets stop. Custom allocators and delete should probably be removed from D:
> Some of my facts:
> * freelist is faster if most allocation and deallocation concentrates on only one
> class. (see attachment) I think this is also the reason it increases DMDs speed.
> Token and Scope are quite obvious bottlenecks..
> * such bottlenecks will most of the time only be detected when development is
> almost finished. (Almost never for library code, so I don't get why STL uses
> custom allocators at all.)
> * premature optimization is evil (see STL custom allocators)
> * late optimization: it is easy if there are custom allocators. In C++ it is even
> trivial. Nice design. Still no clue why STL is abusing it.
> * that form of custom allocators does not play nicely with Ds Garbage collector
> though, because it changes the semantics of 'new', ergo builtin custom allocators
> should probably indeed be removed from D.
> * this makes this form of optimization painful in D without custom allocators.
> This is what I was instinctively scared about. Fact is: it is also painful with
> them, because you don't get the 'delete's for free as in C++. I was somewhat
> inconsiderate on this.
> * it is possible that hinting the GC is only about twice as bad (again, see
> attachment).
> And some notes:
> * the fact that you think all my points were worthless or wrong implies that you
> either did not read all of them or have not considered them yourself when making
> your decision. I think that is scary.

I find it nuts that someone considers blaming/shunning language features just to
mask bad runtime semantics they refuse to fix - but maybe it's just my ignorance
on the subject that professes that view.