Template Metaprogramming Made Easy (Huh?)

Jeremie Pelletier jeremiep at gmail.com
Mon Sep 14 00:18:49 PDT 2009


Nick B Wrote:

> Jeremie Pelletier wrote:
> > Tom S Wrote:
> > 
> >> Jeremie Pelletier wrote:
> >>> Tom S Wrote:
> >>>
> >>>> Jeremie Pelletier wrote:
> >>>>> I myself allocate all my meshes and textures directly on the GC and I'm pretty sure its faster than C's malloc and much safer.
> >>>> Hm, why would it be faster with the GC than malloc? I'm pretty sure it's 
> >>>> the opposite :P Plus, I could use a specialized malloc implementation, 
> >>>> like TLSF.
> >>> The D GC is already specialized, and given its being used quite a lot in D, there are good chances its already sitting in the CPU cache, its heap already having the available memory block waiting on a freelist, or if the alloc is more than 0x1000 bytes, the pages available in a pool. You'd need to use malloc quite a lot to get the same optimal performance, and mixing the two would affect the performance of both.
> >> It might be specialized for _something_, but it definitely isn't 
> >> real-time systems. I'd say with my use cases there's a very poor chance 
> >> the GC is sitting in the CPU cache since most of the time my memory is 
> >> preallocated and managed by specialized structures and/or malloc. I've 
> >> found that using the GC only for the hard-to-manually-manage objects 
> >> works best. The rest is handled by malloc and the GC has a very shallow 
> >> vision of the world thus its collection runs are very fast. Of course 
> >> there's a drawback that both the GC and malloc will have some pages 
> >> cached, wasting memory, but I don't let the GC touch too much so it 
> >> should be minimal. YMMV of course - all depends on the memory allocation 
> >> patterns of the application.
> > 
> > I understand your points for using a separate memory manager, and I agree with you that having less active allocations make for faster sweeps, no matter how little of them are scanned for pointers. However I just had an idea on how to implement generational collection on a non-moving GC which should solve your issues (and well, mines too) with the collector not being fast enough. I need to do some hacking on my custom GC first, but I believe it could give yet another performance boost. I'll add my memory manager to my list of code modules to make public :)
> Jeremie
> 
> If the code is really usefull, why not offer it to the Tango team, for 
> formal inclusion  in the next release ?
> 
> Nick B

Because I dropped support for D1 long ago. If either the Tango or Phobos team like my code once I publish it, they are free to adapt it for their runtime. 

I rewrote the GC from scratch and optimized over the past 2 years to support my custom D runtime. It cannot be used as-is with neither phobos or tango without either changing the public interface of the GC or rewriting every runtime routine calling into the GC. I would only release it to public domain as an example of how to implement a tracing generational non-moving GC. I still need to implement the generational part, but I got the general algorithm down on paper today so I should have it working sometime this week.

I'm not a big fan of code licenses and therefore like to write most of my code myself, if only to learn how it works. I rarely mind people asking for my code either, so long as I get credited for it :)



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