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;
 }