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Use CLK_TCK for clock_nanosleep() spin threshold

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This more accurately reflects how the kernels actually implement this
function and it most importantly avoids incurring startup latency.
This commit is contained in:
Justine Tunney 2023-10-03 16:58:42 -07:00
parent 11c18fa644
commit 695f74035d
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GPG key ID: BE714B4575D6E328
4 changed files with 108 additions and 55 deletions
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72
tool/viz/clock_nanosleep_accuracy.c Normal file
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2023 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/assert.h"
#include "libc/calls/struct/timespec.h"
#include "libc/intrin/kprintf.h"
#include "libc/runtime/runtime.h"
#include "libc/stdio/stdio.h"
#include "libc/sysv/consts/clock.h"
#define MAXIMUM 1e8
#define ITERATIONS 10
void WarmUp(void) {
struct timespec wf = {0, 1};
npassert(!clock_nanosleep(CLOCK_REALTIME, 0, &wf, 0));
}
void TestSleepRealRelative(void) {
printf("\n");
printf("testing: clock_nanosleep(CLOCK_REALTIME) with relative timeout\n");
for (long nanos = 1; nanos < (long)MAXIMUM; nanos *= 2) {
struct timespec t1, t2, wf;
wf = timespec_fromnanos(nanos);
clock_gettime(CLOCK_REALTIME_PRECISE, &t1);
for (int i = 0; i < ITERATIONS; ++i) {
npassert(!clock_nanosleep(CLOCK_REALTIME, 0, &wf, 0));
}
clock_gettime(CLOCK_REALTIME_PRECISE, &t2);
long took = timespec_tonanos(timespec_sub(t2, t1)) / ITERATIONS;
printf("%,11ld ns sleep took %,11ld ns delta %,11ld ns\n", nanos, took,
took - nanos);
}
}
void TestSleepMonoRelative(void) {
printf("\n");
printf("testing: clock_nanosleep(CLOCK_MONOTONIC) with relative timeout\n");
for (long nanos = 1; nanos < (long)MAXIMUM; nanos *= 2) {
struct timespec t1, t2, wf;
wf = timespec_fromnanos(nanos);
clock_gettime(CLOCK_REALTIME_PRECISE, &t1);
for (int i = 0; i < ITERATIONS; ++i) {
npassert(!clock_nanosleep(CLOCK_MONOTONIC, 0, &wf, 0));
}
clock_gettime(CLOCK_REALTIME_PRECISE, &t2);
long took = timespec_tonanos(timespec_sub(t2, t1)) / ITERATIONS;
printf("%,11ld ns sleep took %,11ld ns delta %,11ld ns\n", nanos, took,
took - nanos);
}
}
int main(int argc, char *argv[]) {
WarmUp();
TestSleepRealRelative();
TestSleepMonoRelative();
}