May I chime in? :-) Gents, the current implementation of Python's memory management is really fine and most problems it used to have in the past have been fixed in recent years (at least the ones I know of).
Probably the only one left, indeed, is the potential unbounded growth of int/float objects' freelists (beyond the shared cache of small ints). Yet, this seems to be a questionable problem because any change in the freelists' management will invariably slow down their allocation. By how much, I don't know, but whether you fallback to pymalloc above a certain threshold or use something else, the change will have a generic perf hit. The explanation is simple: you can't beat the free list scheme performance when you have frequent short bursts of allocations and deallocations, which is the typical Python pattern observed on New() & DECREF() calls. BTW if you have 2 AMD combos showing speedups noone can explain in an obvious way, then it's a cache effect. Optimizing pymalloc for non-standard byte-sizes is a no go, and although I've seen suggestions for further optimizations tailored to ints and floats, I haven't seen anyone spelling out what that optimization of pymalloc would consist of. MAL's suggestion to preallocate a pymalloc pool cache for certain object sizes is something I actually implemented in the earliest versions of pymalloc, but eventually dropped in favor of the current dynamic, on-request allocation because pre-allocating pools (and initializing the free lists) costs time and in general leads to degraded performance in the average case. I can't perf this now to prove it, but that was very clear at the time when I wrote the original stuff and applied the regression test on it. So I would kindly suggest to get down to the only problem (if any) which is the uncontrolled growth of the specialized freelists, the shared int cache notwithstanding. If you can limit a degenerative growth without a noticeable generic perf sacrifice, that would sound like an improvement to me, but so far I haven't seen any convincing arguments. And, of course, if the int/float freelist scheme was a real issue we would have probably heard of it by now in a very sound way. Vladimir _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
