83 lines
3.3 KiB
C
83 lines
3.3 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/bits/bits.h"
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#include "libc/bits/initializer.internal.h"
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#include "libc/bits/safemacros.h"
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#include "libc/calls/calls.h"
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#include "libc/dce.h"
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#include "libc/nexgen32e/rdtsc.h"
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#include "libc/nexgen32e/x86feature.h"
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#include "libc/sysv/consts/clock.h"
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#include "libc/time/time.h"
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static struct Now {
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bool once;
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uint64_t k0;
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long double r0, cpn;
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} g_now;
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static long double GetTimeSample(void) {
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uint64_t tick1, tick2;
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long double time1, time2;
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sched_yield();
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time1 = dtime(CLOCK_MONOTONIC);
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tick1 = rdtsc();
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nanosleep(&(struct timespec){0, 100000}, NULL);
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time2 = dtime(CLOCK_MONOTONIC);
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tick2 = rdtsc();
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return (time2 - time1) * 1e9 / MAX(1, tick2 - tick1);
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}
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static long double MeasureNanosPerCycle(void) {
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int i;
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long double avg, samp;
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for (avg = 1.0L, i = 1; i < 5; ++i) {
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samp = GetTimeSample();
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avg += (samp - avg) / i;
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}
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return avg;
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}
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static void InitTime(void) {
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g_now.cpn = MeasureNanosPerCycle();
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g_now.r0 = dtime(CLOCK_REALTIME);
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g_now.k0 = rdtsc();
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g_now.once = true;
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}
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long double converttickstonanos(uint64_t ticks) {
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if (!g_now.once) InitTime();
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return ticks * g_now.cpn; /* pico scale */
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}
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long double converttickstoseconds(uint64_t ticks) {
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return 1 / 1e9 * converttickstonanos(ticks);
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}
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long double nowl$sys(void) {
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return dtime(CLOCK_REALTIME);
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}
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long double nowl$art(void) {
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uint64_t ticks;
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if (!g_now.once) InitTime();
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ticks = unsignedsubtract(rdtsc(), g_now.k0);
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return g_now.r0 + converttickstoseconds(ticks);
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}
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