mirror of
https://github.com/jart/cosmopolitan.git
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115 lines
4 KiB
C
115 lines
4 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.internal.h"
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#include "libc/calls/calls.h"
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#include "libc/calls/clock_gettime.internal.h"
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#include "libc/calls/internal.h"
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#include "libc/calls/state.internal.h"
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#include "libc/calls/strace.internal.h"
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#include "libc/calls/syscall_support-sysv.internal.h"
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#include "libc/dce.h"
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#include "libc/macros.internal.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/str/str.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 clock_gettime_f *__gettime;
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static struct Now {
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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_FAST);
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tick1 = rdtsc();
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nanosleep(&(struct timespec){0, 1000000}, NULL);
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time2 = dtime(CLOCK_MONOTONIC_FAST);
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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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bool tc;
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int i, n;
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long double avg, samp;
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tc = __time_critical;
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__time_critical = true;
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if (IsWindows()) {
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n = 10;
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} else {
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n = 5;
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}
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for (avg = 1.0L, i = 1; i < n; ++i) {
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samp = GetTimeSample();
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avg += (samp - avg) / i;
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}
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__time_critical = tc;
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STRACE("MeasureNanosPerCycle cpn*1000=%d", (long)(avg * 1000));
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return avg;
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}
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void RefreshTime(void) {
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struct Now now;
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now.cpn = MeasureNanosPerCycle();
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now.r0 = dtime(CLOCK_REALTIME);
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now.k0 = rdtsc();
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memcpy(&g_now, &now, sizeof(now));
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}
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static long double nowl_sys(void) {
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return dtime(CLOCK_REALTIME);
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}
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static long double nowl_art(void) {
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uint64_t ticks = rdtsc() - g_now.k0;
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return g_now.r0 + (1 / 1e9L * (ticks * g_now.cpn));
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}
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static long double nowl_vdso(void) {
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long double secs;
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struct timespec tv;
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__gettime(CLOCK_REALTIME, &tv);
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secs = tv.tv_nsec;
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secs *= 1 / 1e9L;
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secs += tv.tv_sec;
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return secs;
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}
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long double nowl_setup(void) {
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bool isfast;
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uint64_t ticks;
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__gettime = __clock_gettime_get(&isfast);
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if (isfast) {
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nowl = nowl_vdso;
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} else if (X86_HAVE(INVTSC)) {
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RefreshTime();
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nowl = nowl_art;
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} else {
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nowl = nowl_sys;
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}
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return nowl();
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}
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