Componentizing D's garbage collector

[deadalnix]

On Friday, 10 January 2014 at 20:37:53 UTC, Rainer Schuetze wrote:
> I think this might help in having different heaps (especially 
> thread local heaps if you include "shared"), but I'm not sure 
> this works in unsafe D where casting is allowed.
>

One of the key to a fast GC is segregating the heap in smaller
parts. This is why generational collectors are so popular in java
for instance.

Segregating the heap imply so complications. For instance, it is
necessary to track reference from one heap to another, typically
from young to older objects.

In D, the type system provide a natural segregation. It would be
a great missed opportunity to not take advantage of it. This
segregation is really nice as pointers go from one to another in
a single direction, avoiding the need to track references
changes, and all element of the heap part share some common
characteristics. These characteristics allow for specialized GC
algorithms (for instance, a GC can run on the immutable heap
without the program even knowing about it).

Casting is by essence bypassing the type system. In this case,
you must be help responsible for what happen. The language cannot
provide guarantees.