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/*-------------------------------------------------------------------------
*
* instr_time.h
* portable high-precision interval timing
*
* This file provides an abstraction layer to hide portability issues in
* interval timing. On Unix we use clock_gettime(), and on Windows we use
* QueryPerformanceCounter(). These macros also give some breathing room to
* use other high-precision-timing APIs.
*
* The basic data type is instr_time, which all callers should treat as an
* opaque typedef. instr_time can store either an absolute time (of
* unspecified reference time) or an interval. The operations provided
* for it are:
*
* INSTR_TIME_IS_ZERO(t) is t equal to zero?
*
* INSTR_TIME_SET_ZERO(t) set t to zero (memset is acceptable too)
*
* INSTR_TIME_SET_CURRENT(t) set t to current time
*
* INSTR_TIME_SET_CURRENT_LAZY(t) set t to current time if t is zero,
* evaluates to whether t changed
*
* INSTR_TIME_ADD(x, y) x += y
*
* INSTR_TIME_SUBTRACT(x, y) x -= y
*
* INSTR_TIME_ACCUM_DIFF(x, y, z) x += (y - z)
*
* INSTR_TIME_GET_DOUBLE(t) convert t to double (in seconds)
*
* INSTR_TIME_GET_MILLISEC(t) convert t to double (in milliseconds)
*
* INSTR_TIME_GET_MICROSEC(t) convert t to uint64 (in microseconds)
*
* INSTR_TIME_GET_NANOSEC(t) convert t to uint64 (in nanoseconds)
*
* Note that INSTR_TIME_SUBTRACT and INSTR_TIME_ACCUM_DIFF convert
* absolute times to intervals. The INSTR_TIME_GET_xxx operations are
* only useful on intervals.
*
* When summing multiple measurements, it's recommended to leave the
* running sum in instr_time form (ie, use INSTR_TIME_ADD or
* INSTR_TIME_ACCUM_DIFF) and convert to a result format only at the end.
*
* Beware of multiple evaluations of the macro arguments.
*
*
* Copyright (c) 2001-2023, PostgreSQL Global Development Group
*
* src/include/portability/instr_time.h
*
*-------------------------------------------------------------------------
*/
#ifndef INSTR_TIME_H
#define INSTR_TIME_H
/*
* We store interval times as an int64 integer on all platforms, as int64 is
* cheap to add/subtract, the most common operation for instr_time. The
* acquisition of time and converting to specific units of time is platform
* specific.
*
* To avoid users of the API relying on the integer representation, we wrap
* the 64bit integer in a struct.
*/
typedef struct instr_time
{
int64 ticks; /* in platforms specific unit */
} instr_time;
/* helpers macros used in platform specific code below */
#define NS_PER_S INT64CONST(1000000000)
#define NS_PER_MS INT64CONST(1000000)
#define NS_PER_US INT64CONST(1000)
#ifndef WIN32
/* Use clock_gettime() */
#include <time.h>
/*
* The best clockid to use according to the POSIX spec is CLOCK_MONOTONIC,
* since that will give reliable interval timing even in the face of changes
* to the system clock. However, POSIX doesn't require implementations to
* provide anything except CLOCK_REALTIME, so fall back to that if we don't
* find CLOCK_MONOTONIC.
*
* Also, some implementations have nonstandard clockids with better properties
* than CLOCK_MONOTONIC. In particular, as of macOS 10.12, Apple provides
* CLOCK_MONOTONIC_RAW which is both faster to read and higher resolution than
* their version of CLOCK_MONOTONIC.
*/
#if defined(__darwin__) && defined(CLOCK_MONOTONIC_RAW)
#define PG_INSTR_CLOCK CLOCK_MONOTONIC_RAW
#elif defined(CLOCK_MONOTONIC)
#define PG_INSTR_CLOCK CLOCK_MONOTONIC
#else
#define PG_INSTR_CLOCK CLOCK_REALTIME
#endif
/* helper for INSTR_TIME_SET_CURRENT */
static inline instr_time
pg_clock_gettime_ns(void)
{
instr_time now;
struct timespec tmp;
clock_gettime(PG_INSTR_CLOCK, &tmp);
now.ticks = tmp.tv_sec * NS_PER_S + tmp.tv_nsec;
return now;
}
#define INSTR_TIME_SET_CURRENT(t) \
((t) = pg_clock_gettime_ns())
#define INSTR_TIME_GET_NANOSEC(t) \
((int64) (t).ticks)
#else /* WIN32 */
/* Use QueryPerformanceCounter() */
/* helper for INSTR_TIME_SET_CURRENT */
static inline instr_time
pg_query_performance_counter(void)
{
instr_time now;
LARGE_INTEGER tmp;
QueryPerformanceCounter(&tmp);
now.ticks = tmp.QuadPart;
return now;
}
static inline double
GetTimerFrequency(void)
{
LARGE_INTEGER f;
QueryPerformanceFrequency(&f);
return (double) f.QuadPart;
}
#define INSTR_TIME_SET_CURRENT(t) \
((t) = pg_query_performance_counter())
#define INSTR_TIME_GET_NANOSEC(t) \
((int64) ((t).ticks * ((double) NS_PER_S / GetTimerFrequency())))
#endif /* WIN32 */
/*
* Common macros
*/
#define INSTR_TIME_IS_ZERO(t) ((t).ticks == 0)
#define INSTR_TIME_SET_ZERO(t) ((t).ticks = 0)
#define INSTR_TIME_SET_CURRENT_LAZY(t) \
(INSTR_TIME_IS_ZERO(t) ? INSTR_TIME_SET_CURRENT(t), true : false)
#define INSTR_TIME_ADD(x,y) \
((x).ticks += (y).ticks)
#define INSTR_TIME_SUBTRACT(x,y) \
((x).ticks -= (y).ticks)
#define INSTR_TIME_ACCUM_DIFF(x,y,z) \
((x).ticks += (y).ticks - (z).ticks)
#define INSTR_TIME_GET_DOUBLE(t) \
((double) INSTR_TIME_GET_NANOSEC(t) / NS_PER_S)
#define INSTR_TIME_GET_MILLISEC(t) \
((double) INSTR_TIME_GET_NANOSEC(t) / NS_PER_MS)
#define INSTR_TIME_GET_MICROSEC(t) \
(INSTR_TIME_GET_NANOSEC(t) / NS_PER_US)
#endif /* INSTR_TIME_H */