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);
Can be quite handy, attempt to provide fallbacks for compilers that don't
support _Static_assert (which is technically a C11 feature). Suppress
warnings as best we can (Clang and GCC warn that we're using a C11 feature
while in C99 mode).
Needs to be tested for MSVC still.
