I haven't been applying many patches recently, partly because I haven't had much time available, and partly because there are gc-related bugs lurking in the code that I regard as higher priority. I tried tracking them down, but somewhere in the middle I realized that I really ought to be trying to put together a 0.0.9 release instead.
So, I just checked in something that breaks 'make test' for everyone: GC_DEBUG is now on by default for tests. (But _only_ for tests -- the parrot executable still has it off by default.) I reworked it so that it is a property of the interpreter and can be enabled and disabled at runtime via the --gc-debug flag to parrot, or by setting the $PARROT_GC_DEBUG environment variable. In fact, it should be possible to toggle it in the middle of a run, but I haven't tried it -- it changes the parameters to the memory management system, so turning it on halfway through a program might do strange stuff. This slows parrot down by about 7% when debugging is turned off (on my machine, for lifetest). So there is also a DISABLE_GC_DEBUG #define in include/parrot/parrot.h that may be turned on for optimized builds. For a -O3 compile on my system, I get a 1% slowdown over the previous CVS version when running without the jit, and a 1% speedup when running with the jit. Or, in other words, no measurable overhead. (Which is unsurprising; it just means I didn't break anything.) I currently get three test failures when running with GC_DEBUG on, but not always the same three (depending on how I muck with unrelated parts of the code.) The slowdown when GC_DEBUG is turned on is... more than 7%. It isn't too bad for most of the tests or mopstest, but for lifetest I get a factor of 140x slowdown. Heh. It also turned out to be too annoyingly slow for t/op/stacks.t test #7 and t/pmc/intlist.t tests #3 and #4. I don't want to make the tests too onerous to run, so I put in a not-so-pretty hack to disable GC_DEBUG for just those three tests, when running under 'make test' or a variant. It's documented in the makefile and in those tests.
