D on next-gen consoles and for game development

[Manu]

On 30 May 2013 19:50, Rainer Schuetze <r.sagitario at gmx.de> wrote:

>
>
> On 29.05.2013 10:06, Manu wrote:
>
>>
>> What do you think is easier, or perhaps even POSSIBLE in D?
>> A good RC approach, or a V8 quality concurrent+incremental GC?
>>
>
> I think none of them is feasible without write-barriers on pointer
> modifications in heap memory. That means extra code needs to be generated
> for each pointer modification (if the compiler cannot optimize it away as
> LLVM seems to be doing in case of Objectve-C). As an alternative, Leandros
> concurrent GC implements them with hardware support by COW, though at a
> pretty large granularity (page size). I'm not sure if this approach can be
> sensibly combined with RC or incremental collection.


I'm talking about embedded hardware. No virtualisation, tight memory limit,
no significant OS. Is it possible?

 I get the feeling either would be acceptable, but I still kinda like
>> idea of the determinism an RC collector offers.
>>
>
> If you want it to be safe and efficient, it needs to use deferred
> reference counting, and this ain't so deterministic anymore. The good thing
> about it is that you usually don't have to scan the whole heap to find
> candidates for reclamation.


Well, it's a bit more deterministic, at least you could depend on the
deferred free happening within a frame let's say, rather than at some
un-knowable future time when the GC feels like performing a collect...

That said, I'd be interested to try it without a deferred free. Performance
impact depends on the amount of temporaries/frees... I don't imagine it
would impact much/at-all since there is so little memory allocation or
pointer assignments in realtime software.
People use horrific C++ smart pointer templates successfully, without any
compiler support at all. It works because the frequency of pointer
assignments is so low.
RC is key to avoid scanning the whole heap, which completely destroys your
dcache.

I reckon this should probably be the next big ticket for D. The
>> long-standing shared library problems seem to be being addressed.
>>
>
> The GC proposed by Leandro looks very promising, though it needs support
> by the hardware and the OS. I think we should see how far we can get with
> this approach.
>

His GC looked good, clearly works better for the sociomantic guys, but I
can't imagine it, or anything like it, will ever work on embedded platforms?
No hardware/OS support... is it possible to emulate the requires features?
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