Allocators in Phobos

[Andrei Alexandrescu]

On 8/22/11 8:36 AM, Steven Schveighoffer wrote:
> On Mon, 22 Aug 2011 09:21:43 -0400, Steven Schveighoffer
> <schveiguy at yahoo.com> wrote:
>
>> On Mon, 22 Aug 2011 09:02:02 -0400, dsimcha <dsimcha at yahoo.com> wrote:
>>
>>> On 8/22/2011 7:07 AM, Steven Schveighoffer wrote:
>>>> Take a look at dcollections' chunk allocator, which is under boost
>>>> license. It implements a free list + efficient allocation/deallocation
>>>> by dividing up a large block. It might be a fit for this, or at least a
>>>> starting point.
>>>>
>>>> One difference from this allocator vs. the generic ones you are
>>>> implementing is that it's templated on the type being allocated. It's
>>>> intended to be used for a collection, which only allocates one type (a
>>>> node). Does this kind of thinking belong in phobos? I'm not sure. But I
>>>> think we can at least reuse the free list implementation.
>>>>
>>>> http://www.dsource.org/projects/dcollections/browser/branches/d2/dcollections/DefaultAllocator.d#L41
>>>>
>>>>
>>>
>>> Hmm, your chunk allocator looks like a generalization of
>>> FreeListAllocator. If I get around to implementing FreeListAllocator,
>>> I'll add support for allocating chunks instead of one element per
>>> heap allocation.
>>
>> Well, I think the GC already uses free lists... What would be the
>> point of one on top of that, especially if the "block size" is constant?
>>
>> https://github.com/D-Programming-Language/druntime/blob/master/src/gc/gcx.d#L505
>>
>> https://github.com/D-Programming-Language/druntime/blob/master/src/gc/gcx.d#L927
>>
>
> I didn't fully read your FreeListAllocator proposal, I lost that it was
> on *top of* another allocator. So obviously, it wouldn't make much sense
> to do it on top of the GC, but it could make sense on top of a different
> allocator (say the C malloc allocator).
>
> In that case, I agree the chunk allocator could be an option for the
> free list allocator.
>
> -Steve

Sorry for writing my answer before reading this.

Andrei