On Thu, Feb 02, 2012 at 08:48:20PM -0600, Robert Jacques wrote: [...]
> So to answer your question, yes, someone has made one of these types of GC for D called CDGC. No, it doesn't look like Windows will support this anytime soon.  And cloning GCs, don't solve the problems of large heaps, soft/hard realtime issues like game render threads, and it actually makes the embarrassingly long pause (when they happen) longer. Now, CDGC, as I understand it, is better written than our current GC and would probably improve things, but I don't see it as the final end goal.

To me, the final goal should be to make the GC swappable, that is, there's a way to tell the compiler which GC you want to use.

After I got convinced about the benefits of GC by the article on garbage collection in DPLO, I started reading up a bit about different GC algorithms, and my conclusion is that there is no such thing as a one-size-fits-all GC.  Every GC algo out there is sensitive to the kind of allocations the program makes, and the memory/speed constraints you're running under. So the real solution to GC performance problems is to make it swappable. Today, for instance, I found a book that talks about a hard real-time GC, which is very different from the paper I mentioned earlier.

The point is, if you want hard real-time guarantees, it should be possible to tell the compiler to use a GC that gives you that, and if you're OK with soft real-time, then you can tell the compiler to use something like CDGC. And if you're writing a batch-processing program you can use a GC with a long STW pause but better overall throughput.

Anyway, I found the blog of the guy who implemented CDGC, and it seems that it did quite well performance-wise at the end. Apparently it's in an experimental D2 branch; anyone tried to use it recently?


T

-- 
Questions are the beginning of intelligence, but the fear of God is the beginning of wisdom.

On 2012-02-03 05:01, H. S. Teoh wrote:
> On Thu, Feb 02, 2012 at 08:48:20PM -0600, Robert Jacques wrote:
> [...]
>> So to answer your question, yes, someone has made one of these types
>> of GC for D called CDGC. No, it doesn't look like Windows will support
>> this anytime soon.  And cloning GCs, don't solve the problems of large
>> heaps, soft/hard realtime issues like game render threads, and it
>> actually makes the embarrassingly long pause (when they happen)
>> longer. Now, CDGC, as I understand it, is better written than our
>> current GC and would probably improve things, but I don't see it as
>> the final end goal.
>
> To me, the final goal should be to make the GC swappable, that is,
> there's a way to tell the compiler which GC you want to use.
>
> After I got convinced about the benefits of GC by the article on garbage
> collection in DPLO, I started reading up a bit about different GC
> algorithms, and my conclusion is that there is no such thing as a
> one-size-fits-all GC.  Every GC algo out there is sensitive to the kind
> of allocations the program makes, and the memory/speed constraints
> you're running under. So the real solution to GC performance problems is
> to make it swappable. Today, for instance, I found a book that talks
> about a hard real-time GC, which is very different from the paper I
> mentioned earlier.
>
> The point is, if you want hard real-time guarantees, it should be
> possible to tell the compiler to use a GC that gives you that, and if
> you're OK with soft real-time, then you can tell the compiler to use
> something like CDGC. And if you're writing a batch-processing program
> you can use a GC with a long STW pause but better overall throughput.
>
> Anyway, I found the blog of the guy who implemented CDGC, and it seems
> that it did quite well performance-wise at the end. Apparently it's in
> an experimental D2 branch; anyone tried to use it recently?
>
>
> T
>

The GC is already swappable during linking.

-- 
/Jacob Carlborg

On Fri, Feb 03, 2012 at 09:30:36AM +0100, Jacob Carlborg wrote: [...]
> The GC is already swappable during linking.
[...]

Is there documentation for this?


T

-- 
No! I'm not in denial!