Microoptimize PyType_Lookup for cache hits #87618
Comments
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The common case going through _PyType_Lookup is to have a cache hit. There's some small tweaks which can make this a little cheaper:
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DinoV
added
3.10
$ ./python -m pyperf compare_to -G --min-speed=3 master.json pytype.json
Slower (1):
- unpack_sequence: 62.2 ns +- 0.6 ns -> 66.1 ns +- 0.9 ns: 1.06x slowerFaster (29):
Benchmark hidden because not significant (30): 2to3, chameleon, genshi_text, genshi_xml, go, hexiom, json_loads, logging_format, meteor_contest, pathlib, pickle_list, python_startup, python_startup_no_site, regex_compile, richards, scimark_sor, sqlalchemy_declarative, sqlalchemy_imperative, sqlite_synth, sympy_expand, sympy_integrate, sympy_sum, sympy_str, tornado_http, unpickle, unpickle_list, xml_etree_parse, xml_etree_iterparse, xml_etree_generate, xml_etree_process Geometric mean: 1.04x faster |
Hey, it's good to see my new pyperf feature being used :-D IMO it helps to more easily compare a large set of benchmarks. |
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Setup a micro-benchmark, foo.c: #define PY_SSIZE_T_CLEAN
#include <Python.h>
#include <string.h>
#include <stdlib.h>
int
main(int argc, char *argv[])
{
wchar_t *program = Py_DecodeLocale(argv[0], NULL);
if (program == NULL) {
fprintf(stderr, "Fatal error: cannot decode argv[0]\n");
exit(1);
}
Py_SetProgramName(program); /* optional but recommended */
Py_Initialize();
PyObject *pName = PyUnicode_DecodeFSDefault("foo");
if (pName == NULL) { printf("no foo\n"); PyErr_Print(); }
PyObject *pModule = PyImport_Import(pName);
if (pModule == NULL) { printf("no mod\n"); PyErr_Print(); return 0; }
PyObject *cls = PyObject_GetAttrString(pModule, "C");
if (cls == NULL) { printf("no cls\n"); }
PyObject *fs[20];
for(int i = 0; i<20; i++) {
char buf[4];
sprintf(buf, "f%d", i);
fs[i] = PyUnicode_DecodeFSDefault(buf);
}
for(int i = 0; i<100000000; i++) {
for(int j = 0; j<20; j++) {
if(_PyType_Lookup(cls, fs[j])==NULL) {
printf("Uh oh\n");
}
}
}
if (Py_FinalizeEx() < 0) {
exit(120);
}
PyMem_RawFree(program);
return 0;
}Lib/foo.py: class C:
pass
for i in range(20):
setattr(C, f"f{i}", lambda self: None)obj hash: 0m6.222s |
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Seems that commit ee48c7d has introduced a regression: |
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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