mirror of https://github.com/python/cpython
df3173d28e
This is strictly about moving the "obmalloc" runtime state from `_PyRuntimeState` to `PyInterpreterState`. Doing so improves isolation between interpreters, specifically most of the memory (incl. objects) allocated for each interpreter's use. This is important for a per-interpreter GIL, but such isolation is valuable even without it. FWIW, a per-interpreter obmalloc is the proverbial canary-in-the-coalmine when it comes to the isolation of objects between interpreters. Any object that leaks (unintentionally) to another interpreter is highly likely to cause a crash (on debug builds at least). That's a useful thing to know, relative to interpreter isolation. |
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| .. | ||
| c_analyzer | ||
| c_common | ||
| c_parser | ||
| cpython | ||
| distutils | ||
| README | ||
| TODO | ||
| c-analyzer.py | ||
| check-c-globals.py | ||
| must-resolve.sh | ||
| table-file.py | ||
README
####################################### # C Globals and CPython Runtime State. CPython's C code makes extensive use of global variables. Each global falls into one of several categories: * (effectively) constants (incl. static types) * globals used exclusively in main or in the REPL * freelists, caches, and counters * process-global state * module state * Python runtime state The ignored-globals.txt file is organized similarly. Of the different categories, the last two are problematic and generally should not exist in the codebase. Globals that hold module state (i.e. in Modules/*.c) cause problems when multiple interpreters are in use. For more info, see PEP 3121, which addresses the situation for extension modules in general. Globals in the last category should be avoided as well. The problem isn't with the Python runtime having state. Rather, the problem is with that state being spread throughout the codebase in dozens of individual globals. Unlike the other globals, the runtime state represents a set of values that are constantly shifting in a complex way. When they are spread out it's harder to get a clear picture of what the runtime involves. Furthermore, when they are spread out it complicates efforts that change the runtime. Consequently, the globals for Python's runtime state have been consolidated under a single top-level _PyRuntime global. No new globals should be added for runtime state. Instead, they should be added to _PyRuntimeState or one of its sub-structs. The check-c-globals script should be run to ensure that no new globals have been added: python3 Tools/c-analyzer/check-c-globals.py You can also use the more generic tool: python3 Tools/c-analyzer/c-analyzer.py If it reports any globals then they should be resolved. If the globals are runtime state then they should be folded into _PyRuntimeState. Otherwise they should be added to ignored-globals.txt.