[issue21148] avoid memset in small tuple creation
Raymond Hettinger added the comment: I think this looks promising. Don't worry too much about the modest timing improvement. For the most part, we should almost always take steps to eliminate work that is known to be unnecessary. The timings serve as a guide but it would be easy for us to get trapped in local minimums on a particular machine or compiler. -- nosy: +rhettinger ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21148 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21148] avoid memset in small tuple creation
STINNER Victor added the comment: avoid memset in small tuple creation I don't understand this title because there is no call to memset() in the patch. Can you try to modify PyTuple_New() to use memset() instead of a dummy loop? Adding a _PyTuple_New() which doesn't initialize the memory doesn't seem safe to me. You may try to allocate the tuple with PyObject_Calloc(), but when I tried on other types, it was slower than PyObject_Malloc() for sizes smaller than 1 MB. -- nosy: +haypo ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21148 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21148] avoid memset in small tuple creation
Changes by Antoine Pitrou pit...@free.fr: -- nosy: +serhiy.storchaka ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21148 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21148] avoid memset in small tuple creation
New submission from Julian Taylor: attached a prototype patch that avoids the memset of ob_item in PyTuple_New which is not necessary for the BUILD_TUPLE bytecode and PyTuple_Pack as these overwrite every entry in ob_item anyway. This improves small tuple creation by about 5%. It does this by adding a new internal function that does not use the memset loop and wrapping that in PyTuple_New that does it. _Pack and ceval call the internal function. The patch still needs cleanup I don't know where the signature for ceval.c would best go. Does the internal function need to be hidden from the DSO? microbenchmark, compiled with gcc-4.8.2 on ubuntu 14.04 amd64, default configure options: import timeit print(min(timeit.repeat((a,), setup=a = 1; b = 1, repeat=5, number=10**7))) print(min(timeit.repeat((a, b), setup=a = 1; b = 1, repeat=5, number=10**7))) before: 0.45767 0.52926 after: 0.42652 0.50122 larger tuples do not profit much as the loading is more expensive in comparison. -- components: Interpreter Core files: avoid-memset.patch keywords: patch messages: 215461 nosy: jtaylor priority: normal severity: normal status: open title: avoid memset in small tuple creation type: performance versions: Python 3.5 Added file: http://bugs.python.org/file34715/avoid-memset.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21148 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21148] avoid memset in small tuple creation
Antoine Pitrou added the comment: A 5% improvement on a micro-benchmark probably means 0% on real workloads. You could try to run the benchmarks suite at http://hg.python.org/benchmarks -- nosy: +pitrou ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21148 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
