bpo-36575: lsprof: Use _PyTime_GetPerfCounter() (GH-8378)

Author: methane

Misc/NEWS.d/next/Library/2019-04-09-22-40-52.bpo-36575.Vg_p92.rst

@@ -0,0 +1,4 @@
+The ``_lsprof`` module now uses internal timer same to ``time.perf_counter()`` by default.
+``gettimeofday(2)`` was used on Unix.  New timer has better resolution on most Unix
+platforms and timings are no longer impacted by system clock updates since ``perf_counter()``
+is monotonic. Patch by Inada Naoki.

Modules/_lsprof.c

@@ -2,62 +2,6 @@
 #include "frameobject.h"
 #include "rotatingtree.h"
 
-/*** Selection of a high-precision timer ***/
-
-#ifdef MS_WINDOWS
-
-#include <windows.h>
-
-static long long
-hpTimer(void)
-{
-    LARGE_INTEGER li;
-    QueryPerformanceCounter(&li);
-    return li.QuadPart;
-}
-
-static double
-hpTimerUnit(void)
-{
-    LARGE_INTEGER li;
-    if (QueryPerformanceFrequency(&li))
-        return 1.0 / li.QuadPart;
-    else
-        return 0.000001;  /* unlikely */
-}
-
-#else  /* !MS_WINDOWS */
-
-#ifndef HAVE_GETTIMEOFDAY
-#error "This module requires gettimeofday() on non-Windows platforms!"
-#endif
-
-#include <sys/resource.h>
-#include <sys/times.h>
-
-static long long
-hpTimer(void)
-{
-    struct timeval tv;
-    long long ret;
-#ifdef GETTIMEOFDAY_NO_TZ
-    gettimeofday(&tv);
-#else
-    gettimeofday(&tv, (struct timezone *)NULL);
-#endif
-    ret = tv.tv_sec;
-    ret = ret * 1000000 + tv.tv_usec;
-    return ret;
-}
-
-static double
-hpTimerUnit(void)
-{
-    return 0.000001;
-}
-
-#endif  /* MS_WINDOWS */
-
 /************************************************************/
 /* Written by Brett Rosen and Ted Czotter */
 
@@ -66,8 +10,8 @@ struct _ProfilerEntry;
 /* represents a function called from another function */
 typedef struct _ProfilerSubEntry {
     rotating_node_t header;
-    long long tt;
-    long long it;
+    _PyTime_t tt;
+    _PyTime_t it;
     long callcount;
     long recursivecallcount;
     long recursionLevel;
@@ -77,17 +21,17 @@ typedef struct _ProfilerSubEntry {
 typedef struct _ProfilerEntry {
     rotating_node_t header;
     PyObject *userObj; /* PyCodeObject, or a descriptive str for builtins */
-    long long tt; /* total time in this entry */
-    long long it; /* inline time in this entry (not in subcalls) */
+    _PyTime_t tt; /* total time in this entry */
+    _PyTime_t it; /* inline time in this entry (not in subcalls) */
     long callcount; /* how many times this was called */
     long recursivecallcount; /* how many times called recursively */
     long recursionLevel;
     rotating_node_t *calls;
 } ProfilerEntry;
 
 typedef struct _ProfilerContext {
-    long long t0;
-    long long subt;
+    _PyTime_t t0;
+    _PyTime_t subt;
     struct _ProfilerContext *previous;
     ProfilerEntry *ctxEntry;
 } ProfilerContext;
@@ -114,41 +58,46 @@ static PyTypeObject PyProfiler_Type;
 
 /*** External Timers ***/
 
-#define DOUBLE_TIMER_PRECISION   4294967296.0
-static PyObject *empty_tuple;
-
-static long long CallExternalTimer(ProfilerObject *pObj)
+static _PyTime_t CallExternalTimer(ProfilerObject *pObj)
 {
-    long long result;
-    PyObject *o = PyObject_Call(pObj->externalTimer, empty_tuple, NULL);
+    PyObject *o = _PyObject_CallNoArg(pObj->externalTimer);
     if (o == NULL) {
         PyErr_WriteUnraisable(pObj->externalTimer);
         return 0;
     }
+
+    _PyTime_t result;
+    int err;
     if (pObj->externalTimerUnit > 0.0) {
         /* interpret the result as an integer that will be scaled
            in profiler_getstats() */
-        result = PyLong_AsLongLong(o);
+        err = _PyTime_FromNanosecondsObject(&result, o);
     }
     else {
         /* interpret the result as a double measured in seconds.
-           As the profiler works with long long internally
+           As the profiler works with _PyTime_t internally
            we convert it to a large integer */
-        double val = PyFloat_AsDouble(o);
-        /* error handling delayed to the code below */
-        result = (long long) (val * DOUBLE_TIMER_PRECISION);
+        err = _PyTime_FromSecondsObject(&result, o, _PyTime_ROUND_FLOOR);
     }
     Py_DECREF(o);
-    if (PyErr_Occurred()) {
+    if (err < 0) {
         PyErr_WriteUnraisable(pObj->externalTimer);
         return 0;
     }
     return result;
 }
 
-#define CALL_TIMER(pObj)        ((pObj)->externalTimer ?                \
-                                        CallExternalTimer(pObj) :       \
-                                        hpTimer())
+static inline _PyTime_t
+call_timer(ProfilerObject *pObj)
+{
+    if (pObj->externalTimer != NULL) {
+        return CallExternalTimer(pObj);
+    }
+    else {
+        return _PyTime_GetPerfCounter();
+    }
+}
+
 
 /*** ProfilerObject ***/
 
@@ -332,14 +281,14 @@ initContext(ProfilerObject *pObj, ProfilerContext *self, ProfilerEntry *entry)
         if (subentry)
             ++subentry->recursionLevel;
     }
-    self->t0 = CALL_TIMER(pObj);
+    self->t0 = call_timer(pObj);
 }
 
 static void
 Stop(ProfilerObject *pObj, ProfilerContext *self, ProfilerEntry *entry)
 {
-    long long tt = CALL_TIMER(pObj) - self->t0;
-    long long it = tt - self->subt;
+    _PyTime_t tt = call_timer(pObj) - self->t0;
+    _PyTime_t it = tt - self->subt;
     if (self->previous)
         self->previous->subt += tt;
     pObj->currentProfilerContext = self->previous;
@@ -631,12 +580,14 @@ profiler_getstats(ProfilerObject *pObj, PyObject* noarg)
     statscollector_t collect;
     if (pending_exception(pObj))
         return NULL;
-    if (!pObj->externalTimer)
-        collect.factor = hpTimerUnit();
-    else if (pObj->externalTimerUnit > 0.0)
+    if (!pObj->externalTimer || pObj->externalTimerUnit == 0.0) {
+        _PyTime_t onesec = _PyTime_FromSeconds(1);
+        collect.factor = (double)1 / onesec;
+    }
+    else {
         collect.factor = pObj->externalTimerUnit;
-    else
-        collect.factor = 1.0 / DOUBLE_TIMER_PRECISION;
+    }
+
     collect.list = PyList_New(0);
     if (collect.list == NULL)
         return NULL;
@@ -882,7 +833,6 @@ PyInit__lsprof(void)
                        (PyObject*) &StatsEntryType);
     PyModule_AddObject(module, "profiler_subentry",
                        (PyObject*) &StatsSubEntryType);
-    empty_tuple = PyTuple_New(0);
     initialized = 1;
     return module;
 }