What are the worst parts of D?

[via Digitalmars-d]

On Thursday, 9 October 2014 at 17:29:01 UTC, Dicebot wrote:
> On Thursday, 9 October 2014 at 16:22:52 UTC, Andrei 
> Alexandrescu wrote:
>>>> To clarify: calling GC.free does remove the root, correct?
>>>
>>> Not before it creates one. When I mean "avoid creating new GC 
>>> roots" I
>>> mean "no GC activity at all other than extending existing 
>>> chunks"
>>
>> That's interesting. So GC.malloc followed by GC.free does 
>> actually affect things negatively?
>
> Yes and quite notably so as GC.malloc can potentially trigger 
> collection. With concurrent GC collection is not a disaster but 
> it still affects the latency and should be avoided.

Is it just the potentially triggered collection, or is the actual 
allocation+deallocation too expensive?

Because the effects of the former can of course be reduced 
greatly by tweaking the GC to not collect every time the heap 
needs to grow, at the cost of slightly more memory consumption.

If it's the latter, that would indicate that maybe a different 
allocator with less overhead needs to be used.

>
>> Also let's note that extending existing chunks may result in 
>> new allocations.
>
> Yes. But as those chunks never get free'd it comes to O(1) 
> allocation count over process lifetime with most allocations 
> happening during program startup / warmup.

Hmm... but shouldn't this just as well apply to the temporary 
allocations? After some warming up phase, the available space on 
the heap should be large enough that all further temporary 
allocations can be satisfied without growing the heap.