Line data    Source code

       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * instr_time.h
       4             :  *    portable high-precision interval timing
       5             :  *
       6             :  * This file provides an abstraction layer to hide portability issues in
       7             :  * interval timing.  On Unix we use clock_gettime(), and on Windows we use
       8             :  * QueryPerformanceCounter().  These macros also give some breathing room to
       9             :  * use other high-precision-timing APIs.
      10             :  *
      11             :  * The basic data type is instr_time, which all callers should treat as an
      12             :  * opaque typedef.  instr_time can store either an absolute time (of
      13             :  * unspecified reference time) or an interval.  The operations provided
      14             :  * for it are:
      15             :  *
      16             :  * INSTR_TIME_IS_ZERO(t)            is t equal to zero?
      17             :  *
      18             :  * INSTR_TIME_SET_ZERO(t)           set t to zero (memset is acceptable too)
      19             :  *
      20             :  * INSTR_TIME_SET_CURRENT(t)        set t to current time
      21             :  *
      22             :  * INSTR_TIME_SET_CURRENT_LAZY(t)   set t to current time if t is zero,
      23             :  *                                  evaluates to whether t changed
      24             :  *
      25             :  * INSTR_TIME_ADD(x, y)             x += y
      26             :  *
      27             :  * INSTR_TIME_SUBTRACT(x, y)        x -= y
      28             :  *
      29             :  * INSTR_TIME_ACCUM_DIFF(x, y, z)   x += (y - z)
      30             :  *
      31             :  * INSTR_TIME_GET_DOUBLE(t)         convert t to double (in seconds)
      32             :  *
      33             :  * INSTR_TIME_GET_MILLISEC(t)       convert t to double (in milliseconds)
      34             :  *
      35             :  * INSTR_TIME_GET_MICROSEC(t)       convert t to uint64 (in microseconds)
      36             :  *
      37             :  * INSTR_TIME_GET_NANOSEC(t)        convert t to uint64 (in nanoseconds)
      38             :  *
      39             :  * Note that INSTR_TIME_SUBTRACT and INSTR_TIME_ACCUM_DIFF convert
      40             :  * absolute times to intervals.  The INSTR_TIME_GET_xxx operations are
      41             :  * only useful on intervals.
      42             :  *
      43             :  * When summing multiple measurements, it's recommended to leave the
      44             :  * running sum in instr_time form (ie, use INSTR_TIME_ADD or
      45             :  * INSTR_TIME_ACCUM_DIFF) and convert to a result format only at the end.
      46             :  *
      47             :  * Beware of multiple evaluations of the macro arguments.
      48             :  *
      49             :  *
      50             :  * Copyright (c) 2001-2024, PostgreSQL Global Development Group
      51             :  *
      52             :  * src/include/portability/instr_time.h
      53             :  *
      54             :  *-------------------------------------------------------------------------
      55             :  */
      56             : #ifndef INSTR_TIME_H
      57             : #define INSTR_TIME_H
      58             : 
      59             : 
      60             : /*
      61             :  * We store interval times as an int64 integer on all platforms, as int64 is
      62             :  * cheap to add/subtract, the most common operation for instr_time. The
      63             :  * acquisition of time and converting to specific units of time is platform
      64             :  * specific.
      65             :  *
      66             :  * To avoid users of the API relying on the integer representation, we wrap
      67             :  * the 64bit integer in a struct.
      68             :  */
      69             : typedef struct instr_time
      70             : {
      71             :     int64       ticks;          /* in platforms specific unit */
      72             : } instr_time;
      73             : 
      74             : 
      75             : /* helpers macros used in platform specific code below */
      76             : 
      77             : #define NS_PER_S    INT64CONST(1000000000)
      78             : #define NS_PER_MS   INT64CONST(1000000)
      79             : #define NS_PER_US   INT64CONST(1000)
      80             : 
      81             : 
      82             : #ifndef WIN32
      83             : 
      84             : 
      85             : /* Use clock_gettime() */
      86             : 
      87             : #include <time.h>
      88             : 
      89             : /*
      90             :  * The best clockid to use according to the POSIX spec is CLOCK_MONOTONIC,
      91             :  * since that will give reliable interval timing even in the face of changes
      92             :  * to the system clock.  However, POSIX doesn't require implementations to
      93             :  * provide anything except CLOCK_REALTIME, so fall back to that if we don't
      94             :  * find CLOCK_MONOTONIC.
      95             :  *
      96             :  * Also, some implementations have nonstandard clockids with better properties
      97             :  * than CLOCK_MONOTONIC.  In particular, as of macOS 10.12, Apple provides
      98             :  * CLOCK_MONOTONIC_RAW which is both faster to read and higher resolution than
      99             :  * their version of CLOCK_MONOTONIC.
     100             :  */
     101             : #if defined(__darwin__) && defined(CLOCK_MONOTONIC_RAW)
     102             : #define PG_INSTR_CLOCK  CLOCK_MONOTONIC_RAW
     103             : #elif defined(CLOCK_MONOTONIC)
     104             : #define PG_INSTR_CLOCK  CLOCK_MONOTONIC
     105             : #else
     106             : #define PG_INSTR_CLOCK  CLOCK_REALTIME
     107             : #endif
     108             : 
     109             : /* helper for INSTR_TIME_SET_CURRENT */
     110             : static inline instr_time
     111    20513580 : pg_clock_gettime_ns(void)
     112             : {
     113             :     instr_time  now;
     114             :     struct timespec tmp;
     115             : 
     116    20513580 :     clock_gettime(PG_INSTR_CLOCK, &tmp);
     117    20513580 :     now.ticks = tmp.tv_sec * NS_PER_S + tmp.tv_nsec;
     118             : 
     119    20513580 :     return now;
     120             : }
     121             : 
     122             : #define INSTR_TIME_SET_CURRENT(t) \
     123             :     ((t) = pg_clock_gettime_ns())
     124             : 
     125             : #define INSTR_TIME_GET_NANOSEC(t) \
     126             :     ((int64) (t).ticks)
     127             : 
     128             : 
     129             : #else                           /* WIN32 */
     130             : 
     131             : 
     132             : /* Use QueryPerformanceCounter() */
     133             : 
     134             : /* helper for INSTR_TIME_SET_CURRENT */
     135             : static inline instr_time
     136             : pg_query_performance_counter(void)
     137             : {
     138             :     instr_time  now;
     139             :     LARGE_INTEGER tmp;
     140             : 
     141             :     QueryPerformanceCounter(&tmp);
     142             :     now.ticks = tmp.QuadPart;
     143             : 
     144             :     return now;
     145             : }
     146             : 
     147             : static inline double
     148             : GetTimerFrequency(void)
     149             : {
     150             :     LARGE_INTEGER f;
     151             : 
     152             :     QueryPerformanceFrequency(&f);
     153             :     return (double) f.QuadPart;
     154             : }
     155             : 
     156             : #define INSTR_TIME_SET_CURRENT(t) \
     157             :     ((t) = pg_query_performance_counter())
     158             : 
     159             : #define INSTR_TIME_GET_NANOSEC(t) \
     160             :     ((int64) ((t).ticks * ((double) NS_PER_S / GetTimerFrequency())))
     161             : 
     162             : #endif                          /* WIN32 */
     163             : 
     164             : 
     165             : /*
     166             :  * Common macros
     167             :  */
     168             : 
     169             : #define INSTR_TIME_IS_ZERO(t)   ((t).ticks == 0)
     170             : 
     171             : 
     172             : #define INSTR_TIME_SET_ZERO(t)  ((t).ticks = 0)
     173             : 
     174             : #define INSTR_TIME_SET_CURRENT_LAZY(t) \
     175             :     (INSTR_TIME_IS_ZERO(t) ? INSTR_TIME_SET_CURRENT(t), true : false)
     176             : 
     177             : 
     178             : #define INSTR_TIME_ADD(x,y) \
     179             :     ((x).ticks += (y).ticks)
     180             : 
     181             : #define INSTR_TIME_SUBTRACT(x,y) \
     182             :     ((x).ticks -= (y).ticks)
     183             : 
     184             : #define INSTR_TIME_ACCUM_DIFF(x,y,z) \
     185             :     ((x).ticks += (y).ticks - (z).ticks)
     186             : 
     187             : 
     188             : #define INSTR_TIME_GET_DOUBLE(t) \
     189             :     ((double) INSTR_TIME_GET_NANOSEC(t) / NS_PER_S)
     190             : 
     191             : #define INSTR_TIME_GET_MILLISEC(t) \
     192             :     ((double) INSTR_TIME_GET_NANOSEC(t) / NS_PER_MS)
     193             : 
     194             : #define INSTR_TIME_GET_MICROSEC(t) \
     195             :     (INSTR_TIME_GET_NANOSEC(t) / NS_PER_US)
     196             : 
     197             : #endif                          /* INSTR_TIME_H */