w00t. An email from matz, and a little spelunking in the ruby subversion repository shows that there’s some tinkering going on in ruby garbage collection land. Here are the interesting change logs:

r15674 | matz | 2008-03-03 01:27:43 -0700 (Mon, 03 Mar 2008) | 5 lines

* gc.c (add_heap): sort heaps array in ascending order to use
  binary search.

* gc.c (is_pointer_to_heap): use binary search to identify object
  in heaps.  works better when number of heap segments grow big.

and

r16194 | matz | 2008-04-25 03:03:32 -0600 (Fri, 25 Apr 2008) | 7 lines

* gc.c (free_unused_heaps): preserve last used heap segment to
  reduce malloc() call.

* gc.c (HEAP_SIZE): use smaller heap segment (2K) for more chance
  to be freed.  based on patch from authorNari .

* gc.c (rb_newobj_from_heap): eventually allocate heap segments.

So now in ruby 1.9 trunk we’re keeping heaps in sorted order by memory address, and using binary search to answer the is_pointer_to_heap() question quickly. This optimizes things to the point where we can really crank down heap size. Smaller heaps means more OS reclaimation, means reduced resource usage, and should even mean a ruby with reduced COW badness. All this at a minimal performance impact for normal execution (maybe none, matz knows).

So applause to open source, and matz specifically for sifting through all the ideas/hacks/and patches to realize this thing. It will be interesting to include 1.9 in the