Hi Stephen,

Out of curiosity, I tried the test case, and here are my results:

MRI 1.8.6 pl 111, memory grows with 80Mb/sec rate (!!!)
Latest MRI 1.8 branch: memory grows with 80Mb/sec rate too
MRI 1.9 - memory doesn't grow
JRuby 1.1RC2 - memory doesn't grow
Rubinius - memory grows at 500Kb/sec

Thanks,
  --Vladimir