Componentizing D's garbage collector

[Dmitry Olshansky]

12-Jan-2014 14:27, Rainer Schuetze пишет:
> On 11.01.2014 22:20, Benjamin Thaut wrote:
>> Am 11.01.2014 21:44, schrieb Andrei Alexandrescu:
>>
>> Well as far as my understanding of GCs goes, you have two options:
>>
>> 1) Impercise pointer discovery => limiting yourself to a mark & sweep
>> 2) Percise pointer disccovery => option to use a semi space GC in
>> combination with a mark & sweep and generations, which allows for
>> superior handling of short lived allocations (which is the biggest
>> problem of D's current GC).
>>
>> Also without percise pointer discovery you will never be able to move
>> objects from one heap into another. This would be especially a problem
>> for the immutable heap, because you might want to allocate all strings
>> on the thread local heap until you discover that you actually need them
>> to be shared between threads. You might also need to move objects into
>> antoher heap whenever a casts happens or global variable is assigned.
>>
>> Kind Regards
>> Benjamin Thaut
>
> I think a moving collector is currently not feasible without restricting
> the language a lot, probably similar to safe D and more. I'm not sure we
> want that in general.

I might be ignorant but why can't we make "mostly-moving" collector?

For that we discern precise pointers (with typeinfo) and conservative 
(such as potential pointers in registers/stack). Then any block pointed 
to by a least one conservative pointer is pinned, others though can be 
moved freely since all of the pointers are known.


-- 
Dmitry Olshansky