Discussion on Go and D

[Rainer Schuetze]

On 4/6/2012 6:20 PM, deadalnix wrote:
> Le 06/04/2012 18:07, Andrei Alexandrescu a écrit :
>> A few more samples of people's perception of the two languages:
>>
>> http://news.ycombinator.com/item?id=3805302
>>
>>
>> Andrei
>
> I did some measurement on that point for D lately :
> http://www.deadalnix.me/2012/03/05/impact-of-64bits-vs-32bits-when-using-non-precise-gc/
>

I studied the GC a bit more and noticed a possible issue:

- memory allocations are aligned up to a power of 2 <= page size
- the memory area beyond the actually requested size is left untouched 
when allocating
- when the memory is collected, it is also untouched
- the marking of references during collection does not know the 
requested size, so it scans the full memory block

Result: When a collected memory block is reused by a smaller allocation, 
there might still be false pointers in the unused area.

When I clear this data, my first impression is that it has improved the 
situation, but not enough. I'll have to create some non-interactive test 
to verify.

Rainer