[issue33930] Segfault with deep recursion into object().__dir__

[INADA Naoki]

INADA Naoki <songofacandy at gmail.com> added the comment:

$ ./python.patched -m perf timeit --compare-to ./python.master -s 'o="foo"' 'o.encode' --duplicate=10000
python.master: ..................... 23.1 ns +- 0.5 ns
python.patched: ..................... 24.6 ns +- 0.5 ns

Mean +- std dev: [python.master] 23.1 ns +- 0.5 ns -> [python.patched] 24.6 ns +- 0.5 ns: 1.06x slower (+6%)

$ perf record ./python.patched -m perf timeit -s 'o="foo"' 'o.encode' --duplicate=10000
Couldn't record kernel reference relocation symbol
Symbol resolution may be skewed if relocation was used (e.g. kexec).
Check /proc/kallsyms permission or run as root.
.....................
Mean +- std dev: 24.9 ns +- 0.7 ns
[ perf record: Woken up 9 times to write data ]
[kernel.kallsyms] with build id debb7f6ce8aad7263cc6564650a88db5c8003389 not found, continuing without symbols
[ perf record: Captured and wrote 2.491 MB perf.data (61787 samples) ]

$ perf report | cat
(snip)
# Total Lost Samples: 0
#
# Samples: 61K of event 'cycles:ppp'
# Event count (approx.): 52880893198
#
# Overhead  Command         Shared Object                                     Symbol
# ........  ..............  ................................................  ..........................................
#
    18.78%  python.patched  python.patched                                    [.] _PyEval_EvalFrameDefault
    14.85%  python.patched  python.patched                                    [.] _PyObject_GenericGetAttrWithDict
     9.93%  python.patched  python.patched                                    [.] PyCFunction_NewEx
     8.56%  python.patched  python.patched                                    [.] _PyType_Lookup
     6.61%  python.patched  python.patched                                    [.] meth_dealloc
     4.12%  python.patched  python.patched                                    [.] PyParser_AddToken
     3.36%  python.patched  python.patched                                    [.] PyObject_GetAttr
     3.33%  python.patched  python.patched                                    [.] PyObject_GC_UnTrack
     3.25%  python.patched  python.patched                                    [.] method_get
     2.92%  python.patched  python.patched                                    [.] _Py_bytes_contains
     2.13%  python.patched  python.patched                                    [.] freechildren
     1.41%  python.patched  python.patched                                    [.] pymalloc_alloc.isra.6.part.7

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue33930>
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