Hi, As far as I know, most amd64 and arm64 systems use only 48bit address spaces. (except [1])
[1] https://software.intel.com/sites/default/files/managed/2b/80/5-level_paging_white_paper.pdf It means there are some chance to compact some data structures. I point two examples below. My question is; can we use 48bit pointer safely? It depends on CPU architecture & OS memory map. Maybe, configure option which is available on only (amd64, amd64) * (Linux, Windows, macOS)? # Possible optimizations by 48bit pointer ## PyASCIIObject [snip] unsigned int ready:1; /* Padding to ensure that PyUnicode_DATA() is always aligned to 4 bytes (see issue #19537 on m68k). */ unsigned int :24; } state; wchar_t *wstr; /* wchar_t representation (null-terminated) */ } PyASCIIObject; Currently, state is 8bit + 24bit padding. I think we can pack state and wstr in 64bit. ## PyDictKeyEntry typedef struct { /* Cached hash code of me_key. */ Py_hash_t me_hash; PyObject *me_key; PyObject *me_value; /* This field is only meaningful for combined tables */ } PyDictKeyEntry; There are chance to compact it: Use only 32bit for hash and 48bit*2 for key and value. CompactEntry may be 16byte instead of 24byte. Regards, -- INADA Naoki <[email protected]> _______________________________________________ Python-Dev mailing list [email protected] https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com