STINNER Victor <vstin...@python.org> added the comment:
Mark: > The problem with having a single immortal `None`, is that it will cause data > cache thrashing as two different CPUs modify the refcount on the shared > `None` object. Yeah, I concur with Mark: having one singleton per interpreter should provide better usage of the CPU caches, especially CPU data cache level 1. Mark: > Consider the case where a thread that doesn't hold the GIL attempts to get a > reference on `None`. The main drawback of PR 18301 is that accessing "Py_None" means accessing tstate->interp->none. Except that the commonly used _PyThreadState_GET() returns NULL if the thread doesn't hold the GIL. One alternative would be to use PyGILState_GetThisThreadState() but this API doesn't support subinterpreters. Maybe we are moving towards a major backward incompatible changes required to make the subinterpreters implementation more efficient. Maybe CPython should have a backward compatible behavior by default (Py_None can be read without holding the GIL), but running subinterpreters in parallel would change Py_None behavior (cannot be read without holding the GIL). I don't know. ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue39511> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
