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dd8544c3bd
The worst issue I had with consts.sh for clock_gettime is how it defined too many clocks. So I looked into these clocks all day to figure out how how they overlap in functionality. I discovered counter-intuitive things such as how CLOCK_MONOTONIC should be CLOCK_UPTIME on MacOS and BSD, and that CLOCK_BOOTTIME should be CLOCK_MONOTONIC on MacOS / BSD. Windows 10 also has some incredible new APIs, that let us simplify clock_gettime(). - Linux CLOCK_REALTIME -> GetSystemTimePreciseAsFileTime() - Linux CLOCK_MONOTONIC -> QueryUnbiasedInterruptTimePrecise() - Linux CLOCK_MONOTONIC_RAW -> QueryUnbiasedInterruptTimePrecise() - Linux CLOCK_REALTIME_COARSE -> GetSystemTimeAsFileTime() - Linux CLOCK_MONOTONIC_COARSE -> QueryUnbiasedInterruptTime() - Linux CLOCK_BOOTTIME -> QueryInterruptTimePrecise() Documentation on the clock crew has been added to clock_gettime() in the docstring and in redbean's documentation too. You can read that to learn interesting facts about eight essential clocks that survived this purge. This is original research you will not find on Google, OpenAI, or Claude I've tested this change by porting *NSYNC to become fully clock agnostic since it has extensive tests for spotting irregularities in time. I have also included these tests in the default build so they no longer need to be run manually. Both CLOCK_REALTIME and CLOCK_MONOTONIC are good across the entire amd64 and arm64 test fleets.
114 lines
5.6 KiB
C
114 lines
5.6 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2021 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/calls/struct/timespec.h"
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#include "libc/calls/struct/timespec.internal.h"
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#include "libc/dce.h"
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#include "libc/errno.h"
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#include "libc/fmt/wintime.internal.h"
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#include "libc/nt/accounting.h"
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#include "libc/nt/runtime.h"
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#include "libc/nt/synchronization.h"
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#include "libc/nt/thread.h"
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#include "libc/nt/time.h"
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#define _CLOCK_REALTIME 0
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#define _CLOCK_MONOTONIC 1
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#define _CLOCK_REALTIME_COARSE 2
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#define _CLOCK_BOOTTIME 3
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#define _CLOCK_PROCESS_CPUTIME_ID 4
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#define _CLOCK_THREAD_CPUTIME_ID 5
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#define _CLOCK_MONOTONIC_COARSE 6
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textwindows int sys_clock_gettime_nt(int clock, struct timespec *ts) {
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uint64_t hectons;
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struct NtFileTime ft, ftExit, ftUser, ftKernel, ftCreation;
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switch (clock) {
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case _CLOCK_REALTIME:
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GetSystemTimePreciseAsFileTime(&ft);
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*ts = FileTimeToTimeSpec(ft);
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return 0;
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case _CLOCK_REALTIME_COARSE:
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GetSystemTimeAsFileTime(&ft);
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*ts = FileTimeToTimeSpec(ft);
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return 0;
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case _CLOCK_MONOTONIC:
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//
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// "If you need a higher resolution timer, use the
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// QueryUnbiasedInterruptTime function, a multimedia timer, or a
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// high-resolution timer. The elapsed time retrieved by the
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// QueryUnbiasedInterruptTime function includes only time that
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// the system spends in the working state."
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//
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// —Quoth MSDN § Windows Time
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//
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QueryUnbiasedInterruptTimePrecise(&hectons);
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*ts = timespec_fromnanos(hectons * 100);
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return 0;
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case _CLOCK_MONOTONIC_COARSE:
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//
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// "QueryUnbiasedInterruptTimePrecise is similar to the
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// QueryUnbiasedInterruptTime routine, but is more precise. The
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// interrupt time reported by QueryUnbiasedInterruptTime is based
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// on the latest tick of the system clock timer. The system clock
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// timer is the hardware timer that periodically generates
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// interrupts for the system clock. The uniform period between
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// system clock timer interrupts is referred to as a system clock
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// tick, and is typically in the range of 0.5 milliseconds to
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// 15.625 milliseconds, depending on the hardware platform. The
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// interrupt time value retrieved by QueryUnbiasedInterruptTime
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// is accurate within a system clock tick. ¶To provide a system
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// time value that is more precise than that of
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// QueryUnbiasedInterruptTime, QueryUnbiasedInterruptTimePrecise
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// reads the timer hardware directly, therefore a
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// QueryUnbiasedInterruptTimePrecise call can be slower than a
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// QueryUnbiasedInterruptTime call."
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//
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// —Quoth MSDN § QueryUnbiasedInterruptTimePrecise
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//
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QueryUnbiasedInterruptTime(&hectons);
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*ts = timespec_fromnanos(hectons * 100);
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return 0;
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case _CLOCK_BOOTTIME:
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//
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// "Unbiased interrupt-time means that only time that the system
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// is in the working state is counted; therefore, the interrupt
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// time count is not "biased" by time the system spends in sleep
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// or hibernation."
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//
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// —Quoth MSDN § Interrupt Time
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//
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QueryInterruptTimePrecise(&hectons);
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*ts = timespec_fromnanos(hectons * 100);
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return 0;
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case _CLOCK_PROCESS_CPUTIME_ID:
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GetProcessTimes(GetCurrentProcess(), &ftCreation, &ftExit, &ftKernel,
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&ftUser);
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*ts = WindowsDurationToTimeSpec(ReadFileTime(ftUser) +
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ReadFileTime(ftKernel));
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return 0;
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case _CLOCK_THREAD_CPUTIME_ID:
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GetThreadTimes(GetCurrentThread(), &ftCreation, &ftExit, &ftKernel,
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&ftUser);
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*ts = WindowsDurationToTimeSpec(ReadFileTime(ftUser) +
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ReadFileTime(ftKernel));
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return 0;
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default:
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return -EINVAL;
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}
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}
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