From d4825ac27cba68d02221e13910ea42ee9caac38c Mon Sep 17 00:00:00 2001 From: Jeffrey Bosboom Date: Tue, 9 Sep 2025 02:05:54 -0700 Subject: [PATCH] gh-138535: Optimize fill_time for typical timestamps (#138537) While file timestamps can be anything the file system can store, most lie between the recent past and the near future. Optimize fill_time() for typical timestamps in three ways: - When possible, convert to nanoseconds with C arithmetic. - When using C arithmetic and the seconds member is not required (for st_birthtime), avoid creating a long object. - When using C arithmetic, reorder the code to avoid the null checks implied in Py_XDECREF(). Co-authored-by: Victor Stinner --- Lib/test/test_os.py | 12 ++- ...-09-06-20-09-32.gh-issue-138535.mlntEe.rst | 2 + Modules/posixmodule.c | 89 +++++++++++-------- 3 files changed, 62 insertions(+), 41 deletions(-) create mode 100644 Misc/NEWS.d/next/Library/2025-09-06-20-09-32.gh-issue-138535.mlntEe.rst diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py index b476b431ad6f..cd15aa10f16d 100644 --- a/Lib/test/test_os.py +++ b/Lib/test/test_os.py @@ -1064,9 +1064,15 @@ class UtimeTests(unittest.TestCase): if self.get_file_system(self.dirname) != "NTFS": self.skipTest("requires NTFS") - large = 5000000000 # some day in 2128 - os.utime(self.fname, (large, large)) - self.assertEqual(os.stat(self.fname).st_mtime, large) + times = ( + 5000000000, # some day in 2128 + # boundaries of the fast path cutoff in posixmodule.c:fill_time + -9223372037, -9223372036, 9223372035, 9223372036, + ) + for large in times: + with self.subTest(large=large): + os.utime(self.fname, (large, large)) + self.assertEqual(os.stat(self.fname).st_mtime, large) def test_utime_invalid_arguments(self): # seconds and nanoseconds parameters are mutually exclusive diff --git a/Misc/NEWS.d/next/Library/2025-09-06-20-09-32.gh-issue-138535.mlntEe.rst b/Misc/NEWS.d/next/Library/2025-09-06-20-09-32.gh-issue-138535.mlntEe.rst new file mode 100644 index 000000000000..3fa8f48d56a2 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2025-09-06-20-09-32.gh-issue-138535.mlntEe.rst @@ -0,0 +1,2 @@ +Speed up :func:`os.stat` for files with reasonable timestamps. Contributed +by Jeffrey Bosboom. diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c index 53b21e993764..74edd28998b5 100644 --- a/Modules/posixmodule.c +++ b/Modules/posixmodule.c @@ -2588,55 +2588,68 @@ static int fill_time(PyObject *module, PyObject *v, int s_index, int f_index, int ns_index, time_t sec, unsigned long nsec) { assert(!PyErr_Occurred()); - - int res = -1; - PyObject *s_in_ns = NULL; - PyObject *ns_total = NULL; - PyObject *float_s = NULL; - - PyObject *s = _PyLong_FromTime_t(sec); - PyObject *ns_fractional = PyLong_FromUnsignedLong(nsec); - if (!(s && ns_fractional)) { - goto exit; - } - - s_in_ns = PyNumber_Multiply(s, get_posix_state(module)->billion); - if (!s_in_ns) { - goto exit; - } - - ns_total = PyNumber_Add(s_in_ns, ns_fractional); - if (!ns_total) - goto exit; - - float_s = PyFloat_FromDouble(sec + 1e-9*nsec); - if (!float_s) { - goto exit; - } +#define SEC_TO_NS (1000000000LL) + assert(nsec < SEC_TO_NS); if (s_index >= 0) { + PyObject *s = _PyLong_FromTime_t(sec); + if (s == NULL) { + return -1; + } PyStructSequence_SET_ITEM(v, s_index, s); - s = NULL; } + if (f_index >= 0) { + PyObject *float_s = PyFloat_FromDouble((double)sec + 1e-9 * nsec); + if (float_s == NULL) { + return -1; + } PyStructSequence_SET_ITEM(v, f_index, float_s); - float_s = NULL; } + + int res = -1; if (ns_index >= 0) { - PyStructSequence_SET_ITEM(v, ns_index, ns_total); - ns_total = NULL; - } + /* 1677-09-21 00:12:44 to 2262-04-11 23:47:15 UTC inclusive */ + if ((LLONG_MIN/SEC_TO_NS) <= sec && sec <= (LLONG_MAX/SEC_TO_NS - 1)) { + PyObject *ns_total = PyLong_FromLongLong(sec * SEC_TO_NS + nsec); + if (ns_total == NULL) { + return -1; + } + PyStructSequence_SET_ITEM(v, ns_index, ns_total); + assert(!PyErr_Occurred()); + res = 0; + } + else { + PyObject *s_in_ns = NULL; + PyObject *ns_total = NULL; + PyObject *s = _PyLong_FromTime_t(sec); + PyObject *ns_fractional = PyLong_FromUnsignedLong(nsec); + if (s == NULL || ns_fractional == NULL) { + goto exit; + } - assert(!PyErr_Occurred()); - res = 0; + s_in_ns = PyNumber_Multiply(s, get_posix_state(module)->billion); + if (s_in_ns == NULL) { + goto exit; + } + + ns_total = PyNumber_Add(s_in_ns, ns_fractional); + if (ns_total == NULL) { + goto exit; + } + PyStructSequence_SET_ITEM(v, ns_index, ns_total); + assert(!PyErr_Occurred()); + res = 0; + + exit: + Py_XDECREF(s); + Py_XDECREF(ns_fractional); + Py_XDECREF(s_in_ns); + } + } -exit: - Py_XDECREF(s); - Py_XDECREF(ns_fractional); - Py_XDECREF(s_in_ns); - Py_XDECREF(ns_total); - Py_XDECREF(float_s); return res; + #undef SEC_TO_NS } #ifdef MS_WINDOWS -- 2.47.3