STINNER Victor <vstin...@python.org> added the comment:
There are many ways to get the current interpreter (interp) and the current Python thread state (tstate). Public C API, opaque function call: * PyInterpreterState_Get() (new in Python 3.9) * PyThreadState_Get() Internal C API, static inline functions: * _PyInterpreterState_GET() * _PyThreadState_GET() There are so many variants that I wrote notes for myself: https://pythondev.readthedocs.io/pystate.html This issue is about optimizing _PyInterpreterState_GET() and _PyThreadState_GET() which are supposed to be the most efficient implementations. Currently, _PyInterpreterState_GET() is implemented as _PyThreadState_GET()->interp, and _PyThreadState_GET() is implemented as: _Py_atomic_load_relaxed(_PyRuntime.gilstate.tstate_current) -- To find the _PyInterpreterState_GET() machine code, I read the PyInterpreterState_Get() assembly code (not optimized, it adds tstate==NULL test) and PyTuple_New() assembly code, since PyTuple_New() now needs to get the current interpreter: static struct _Py_tuple_state * get_tuple_state(void) { PyInterpreterState *interp = _PyInterpreterState_GET(); return &interp->tuple; } To find the _PyThreadState_GET() machine code, I read the PyThreadState_Get() assembly code. I looked at the x86-64 machine code generated by GCC -O3 (no LTO, no PGO, it should not be relevant here), using GCC 10.2.1 on Fedora 33. _PyThreadState_GET(): mov rax,QWORD PTR [rip+0x2292b1] # 0x743118 <_PyRuntime+568> _PyInterpreterState_GET(): mov rax,QWORD PTR [rip+0x22a7dd] # 0x743118 <_PyRuntime+568> mov rax,QWORD PTR [rax+0x10] By default, Python is built with -fPIC: _PyRuntime variable does not have a fixed address. $ objdump -t ./python|grep '\<_PyRuntime\>' 0000000000742ee0 g O .bss 00000000000002a0 _PyRuntime The "[rip+0x2292b1] # 0x743118 <_PyRuntime+568>" indirection is needed by PIC. ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue40522> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
