New submission from STINNER Victor: When analyzing results of Python performance benchmarks, I noticed that call_method was 70% slower (!) between revisions 83877018ef97 (Oct 18) and 3e073e7b4460 (Oct 22), including these revisions, on the speed-python server.
On these revisions, the CPU L1 instruction cache is less efficient: 8% cache misses, whereas it was only 0.06% before and after these revisions. Since the two mentioned revisions have no obvious impact on the call_method() benchmark, I understand that the performance difference by a different layout of the machine code, maybe the exact location of functions. IMO the best solution to such compilation issue is to use PGO compilation. Problem: PGO doesn't work on Ubuntu 14.04, the OS used by speed-python (the server runining benchmarks for http://speed.python.org/). I propose to decorate manually the "hot" functions using the GCC __attribute__((hot)) decorator: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes (search for "hot") Attached patch adds Py_HOT_FUNCTION and decorates the following functions: * _PyEval_EvalFrameDefault() * PyFrame_New() * call_function() * lookdict_unicode_nodummy() * _PyFunction_FastCall() * frame_dealloc() These functions are the top 6 according to the Linux perf tool when running the call_simple benchmark of the performance project: 32,66%: _PyEval_EvalFrameDefault 13,09%: PyFrame_New 12,78%: call_function 12,24%: lookdict_unicode_nodummy 9,85%: _PyFunction_FastCall 8,47%: frame_dealloc ---------- components: Interpreter Core files: hot_function.patch keywords: patch messages: 280097 nosy: haypo priority: normal severity: normal status: open title: Decorate hot functions using __attribute__((hot)) to optimize Python type: performance versions: Python 3.7 Added file: http://bugs.python.org/file45361/hot_function.patch _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue28618> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
