There are indeed two symbols used for debugging; one is CACHED_LOOKUP_STATS (Python/ceval.c) that outputs the hit/miss ratios for the cache when python exits and the other is LOOKUP_DEBUG_TIMESTAMP_LIMIT (Objects/dictobject.c) that forces the global counter to wrap around every 10000 dict changes (instead of every 2**32 dict changes).

Actually on this patch I'm getting confusing results on my machine (for example getting better results with statistics ON, that to me just make no sense at all). I got no results from anyone else so I can't say if this patch is actually speeding up or slowing down python. On my machine (trunk python) pystone gets 1.8 seconds without stats, 1.6 seconds with stats (!) and 1.7 seconds without the patch applied.

Does anyone have the time to check on their setup/machines ? So far I'm quite confused...