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viml/profile: switch to uv_gettimeofday() #10356

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Performance of high-resolution time (clock_gettime via uv_hrtime) is
expensive on some systems.  For profiling VimL, syntax, etc., we don't
care about nanosecond-precision and monotonicity edge-cases, so avoid
uv_hrtime().

closes #10328

From the uv__hrtime() source:
0cdb4a5b4b/src/unix/linux-core.c (L442-L462)

    /* Prefer CLOCK_MONOTONIC_COARSE if available but only when it has
     * millisecond granularity or better.  CLOCK_MONOTONIC_COARSE is
     * serviced entirely from the vDSO, whereas CLOCK_MONOTONIC may
     * decide to make a costly system call.
     */

This micro-benchmark (Debug build) shows negligible differences on my
system:

    #include <sys/time.h>
    ...

    proftime_T tm = profile_start();
    int trials = 999999;
    int64_t t = 0;
    struct timeval tv;
    for (int i = 0; i < trials; i++) {
      t += gettimeofday(&tv,NULL);
    }
    tm = profile_end(tm);
    ILOG("%d trials of gettimeofday: %s", trials, profile_msg(tm));
    tm = profile_start();
    for (int i = 0; i < trials; i++) {
      t += os_hrtime();
    }
    tm = profile_end(tm);
    ILOG("%d trials of os_hrtime: %s", trials, profile_msg(tm));
    tm = profile_start();
    for (int i = 0; i < trials; i++) {
      t += os_utime();
    }
    tm = profile_end(tm);
    ILOG("%d trials of os_utime: %s", trials, profile_msg(tm));
    ILOG("%zu", t);
This commit is contained in:
Justin M. Keyes 2019-06-29 16:39:22 +02:00 committed by GitHub
parent 23a9794920
commit e2ce5ff9d6
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GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 84 additions and 50 deletions
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7
src/nvim/assert.h
View File

@ -133,8 +133,10 @@
/// Alternative for compilers without __builtin_xx_overflow ?
/// https://stackoverflow.com/a/44830670/152142
///
/// @param MAX Maximum value of the narrowest type of operand.
/// Not used if compiler supports __builtin_add_overflow.
/// @param a Operand 1.
/// @param b Operand 2.
/// @param c Where to store the result.
/// @param t Result type. Not used if compiler supports __builtin_add_overflow.
#ifdef HAVE_BUILTIN_ADD_OVERFLOW
# define STRICT_ADD(a, b, c, t) \
do { \
@ -150,6 +152,7 @@
/// @def STRICT_SUB
/// @brief Subtracts (a - b) and stores result in `c`. Aborts on overflow.
/// @see STRICT_ADD
#ifdef HAVE_BUILTIN_ADD_OVERFLOW
# define STRICT_SUB(a, b, c, t) \
do { \

2
src/nvim/eval.c
View File

@ -16536,7 +16536,7 @@ static void f_reltimefloat(typval_T *argvars , typval_T *rettv, FunPtr fptr)
rettv->v_type = VAR_FLOAT;
rettv->vval.v_float = 0;
if (list2proftime(&argvars[0], &tm) == OK) {
rettv->vval.v_float = ((float_T)tm) / 1000000000;
rettv->vval.v_float = ((float_T)tm) / 1000000;
}
}

46
src/nvim/os/time.c
View File

@ -9,6 +9,7 @@
#include <uv.h>
#include "nvim/assert.h"
#include "nvim/os/time.h"
#include "nvim/os/input.h"
#include "nvim/event/loop.h"
@ -22,6 +23,7 @@ static uv_cond_t delay_cond;
#ifdef INCLUDE_GENERATED_DECLARATIONS
# include "os/time.c.generated.h"
#endif
/// Initializes the time module
void time_init(void)
{
@ -29,15 +31,53 @@ void time_init(void)
uv_cond_init(&delay_cond);
}
/// Obtain a high-resolution timer value
/// Gets the current time with microsecond (μs) precision.
///
/// @return a timer value, not related to the time of day and not subject
/// to clock drift. The value is expressed in nanoseconds.
/// Subject to system-clock quirks (drift, going backwards, skipping).
/// But it is much faster than os_hrtime() on some systems. #10328
///
/// @see gettimeofday(2)
///
/// @return Current time in microseconds.
uint64_t os_utime(void)
FUNC_ATTR_WARN_UNUSED_RESULT
{
uv_timeval64_t tm;
int e = uv_gettimeofday(&tm);
if (e != 0 || tm.tv_sec < 0 || tm.tv_usec < 0) {
return 0;
}
uint64_t rv = (uint64_t)tm.tv_sec * 1000 * 1000; // s => μs
STRICT_ADD(rv, tm.tv_usec, &rv, uint64_t);
return rv;
}
/// Gets a high-resolution (nanosecond), monotonically-increasing time relative
/// to an arbitrary time in the past.
///
/// Not related to the time of day and therefore not subject to clock drift.
///
/// @return Relative time value with nanosecond precision.
uint64_t os_hrtime(void)
FUNC_ATTR_WARN_UNUSED_RESULT
{
return uv_hrtime();
}
/// Gets a millisecond-resolution, monotonically-increasing time relative to an
/// arbitrary time in the past.
///
/// Not related to the time of day and therefore not subject to clock drift.
/// The value is cached by the loop, it will not change until the next
/// loop-tick (unless uv_update_time is called).
///
/// @return Relative time value with millisecond precision.
uint64_t os_now(void)
FUNC_ATTR_WARN_UNUSED_RESULT
{
return uv_now(&main_loop.uv);
}
/// Sleeps for `ms` milliseconds.
///
/// @param ms Number of milliseconds to sleep

79
src/nvim/profile.c
View File

@ -16,43 +16,38 @@
# include "profile.c.generated.h"
#endif
/// functions for profiling
static proftime_T prof_wait_time;
/// profile_start - return the current time
/// Gets the current time.
///
/// @return the current time
proftime_T profile_start(void) FUNC_ATTR_WARN_UNUSED_RESULT
{
return os_hrtime();
return os_utime();
}
/// profile_end - compute the time elapsed
/// Computes the time elapsed.
///
/// @return the elapsed time from `tm` until now.
/// @return Elapsed time from `tm` until now.
proftime_T profile_end(proftime_T tm) FUNC_ATTR_WARN_UNUSED_RESULT
{
return os_hrtime() - tm;
return profile_sub(os_utime(), tm);
}
/// profile_msg - return a string that represents the time in `tm`
/// Gets a string representing time `tm`.
///
/// @warning Do not modify or free this string, not multithread-safe.
///
/// @param tm The time to be represented
/// @return a static string representing `tm` in the
/// form "seconds.microseconds".
/// @param tm Time
/// @return Static string representing `tm` in the form "seconds.microseconds".
const char *profile_msg(proftime_T tm) FUNC_ATTR_WARN_UNUSED_RESULT
{
static char buf[50];
snprintf(buf, sizeof(buf), "%10.6lf", (double)tm / 1000000000.0);
snprintf(buf, sizeof(buf), "%10.6lf", (double)tm / 1000000.0);
return buf;
}
/// profile_setlimit - return the time `msec` into the future
/// Gets the time `msec` into the future.
///
/// @param msec milliseconds, the maximum number of milliseconds is
/// (2^63 / 10^6) - 1 = 9.223372e+12.
@ -64,14 +59,13 @@ proftime_T profile_setlimit(int64_t msec) FUNC_ATTR_WARN_UNUSED_RESULT
// no limit
return profile_zero();
}
assert(msec <= (INT64_MAX / 1000LL) - 1);
assert(msec <= (INT64_MAX / 1000000LL) - 1);
proftime_T nsec = (proftime_T) msec * 1000000ULL;
return os_hrtime() + nsec;
proftime_T usec = (proftime_T)msec * 1000ULL;
return os_utime() + usec;
}
/// profile_passed_limit - check if current time has passed `tm`
/// Checks if current time has passed `tm`.
///
/// @return true if the current time is past `tm`, false if not or if the
/// timer was not set.
@ -81,11 +75,10 @@ bool profile_passed_limit(proftime_T tm) FUNC_ATTR_WARN_UNUSED_RESULT
// timer was not set
return false;
}
return profile_cmp(os_hrtime(), tm) < 0;
return profile_cmp(os_utime(), tm) < 0;
}
/// profile_zero - obtain the zero time
/// Gets the zero time.
///
/// @return the zero time
proftime_T profile_zero(void) FUNC_ATTR_CONST
@ -93,7 +86,7 @@ proftime_T profile_zero(void) FUNC_ATTR_CONST
return 0;
}
/// profile_divide - divide the time `tm` by `count`.
/// Divides time `tm` by `count`.
///
/// @return 0 if count <= 0, otherwise tm / count
proftime_T profile_divide(proftime_T tm, int count) FUNC_ATTR_CONST
@ -105,7 +98,7 @@ proftime_T profile_divide(proftime_T tm, int count) FUNC_ATTR_CONST
return (proftime_T) round((double) tm / (double) count);
}
/// profile_add - add the time `tm2` to `tm1`
/// Adds time `tm2` to `tm1`.
///
/// @return `tm1` + `tm2`
proftime_T profile_add(proftime_T tm1, proftime_T tm2) FUNC_ATTR_CONST
@ -113,16 +106,15 @@ proftime_T profile_add(proftime_T tm1, proftime_T tm2) FUNC_ATTR_CONST
return tm1 + tm2;
}
/// profile_sub - subtract `tm2` from `tm1`
/// Subtracts time `tm2` from `tm1`.
///
/// @return `tm1` - `tm2`
proftime_T profile_sub(proftime_T tm1, proftime_T tm2) FUNC_ATTR_CONST
{
return tm1 - tm2;
return tm1 > tm2 ? tm1 - tm2 : 0; // os_utime() may go backwards.
}
/// profile_self - add the `self` time from the total time and the
/// children's time
/// Adds the `self` time from the total time and the `children` time.
///
/// @return if `total` <= `children`, then self, otherwise `self` + `total` -
/// `children`
@ -139,7 +131,7 @@ proftime_T profile_self(proftime_T self, proftime_T total, proftime_T children)
return profile_sub(profile_add(self, total), children);
}
/// profile_get_wait - get the current waittime
/// Gets the current waittime.
///
/// @return the current waittime
proftime_T profile_get_wait(void) FUNC_ATTR_PURE
@ -147,13 +139,13 @@ proftime_T profile_get_wait(void) FUNC_ATTR_PURE
return prof_wait_time;
}
/// profile_set_wait - set the current waittime
/// Sets the current waittime.
void profile_set_wait(proftime_T wait)
{
prof_wait_time = wait;
}
/// profile_sub_wait - subtract the passed waittime since `tm`
/// Subtracts the passed waittime since `tm`.
///
/// @return `tma` - (waittime - `tm`)
proftime_T profile_sub_wait(proftime_T tm, proftime_T tma) FUNC_ATTR_PURE
@ -162,7 +154,7 @@ proftime_T profile_sub_wait(proftime_T tm, proftime_T tma) FUNC_ATTR_PURE
return profile_sub(tma, tm3);
}
/// profile_equal - check if `tm1` is equal to `tm2`
/// Checks if time `tm1` is equal to `tm2`.
///
/// @return true if `tm1` == `tm2`
bool profile_equal(proftime_T tm1, proftime_T tm2) FUNC_ATTR_CONST
@ -170,7 +162,7 @@ bool profile_equal(proftime_T tm1, proftime_T tm2) FUNC_ATTR_CONST
return tm1 == tm2;
}
/// sgn64 - calculates the sign of a 64-bit integer
/// Calculates the sign of a 64-bit integer.
///
/// @return -1, 0, or +1
static inline int sgn64(int64_t x) FUNC_ATTR_CONST
@ -178,10 +170,9 @@ static inline int sgn64(int64_t x) FUNC_ATTR_CONST
return (int) ((x > 0) - (x < 0));
}
/// profile_cmp - compare profiling times
/// Compares profiling times.
///
/// Only guarantees correct results if both input times are not more than
/// 150 years apart.
/// Times `tm1` and `tm2` must be less than 150 years apart.
///
/// @return <0, 0 or >0 if `tm2` < `tm1`, `tm2` == `tm1` or `tm2` > `tm1`
int profile_cmp(proftime_T tm1, proftime_T tm2) FUNC_ATTR_CONST
@ -193,7 +184,7 @@ int profile_cmp(proftime_T tm1, proftime_T tm2) FUNC_ATTR_CONST
static proftime_T g_start_time;
static proftime_T g_prev_time;
/// time_push - save the previous time before doing something that could nest
/// Saves the previous time before doing something that could nest.
///
/// After calling this function, the static global `g_prev_time` will
/// contain the current time.
@ -212,7 +203,7 @@ void time_push(proftime_T *rel, proftime_T *start)
g_prev_time = now;
}
/// time_pop - compute the prev time after doing something that could nest
/// Computes the prev time after doing something that could nest.
///
/// Subtracts `tp` from the static global `g_prev_time`.
///
@ -222,18 +213,18 @@ void time_pop(proftime_T tp)
g_prev_time -= tp;
}
/// time_diff - print the difference between `then` and `now`
/// Prints the difference between `then` and `now`.
///
/// the format is "msec.usec".
static void time_diff(proftime_T then, proftime_T now)
{
proftime_T diff = profile_sub(now, then);
fprintf(time_fd, "%07.3lf", (double) diff / 1.0E6);
fprintf(time_fd, "%07.3lf", (double)diff / 1.0E3);
}
/// time_start - initialize the startuptime code
/// Initializes the startuptime code.
///
/// Needs to be called once before calling other startuptime code (such as
/// Must be called once before calling other startuptime code (such as
/// time_{push,pop,msg,...}).
///
/// @param message the message that will be displayed
@ -253,7 +244,7 @@ void time_start(const char *message)
time_msg(message, NULL);
}
/// time_msg - print out timing info
/// Prints out timing info.
///
/// @warning don't forget to call `time_start()` once before calling this.
///