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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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80
libc/runtime/clktck.c
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@ -1,80 +0,0 @@
/*-*- 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 2021 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/runtime/clktck.h"
#include "libc/calls/calls.h"
#include "libc/dce.h"
#include "libc/fmt/wintime.internal.h"
#include "libc/intrin/getauxval.internal.h"
#include "libc/runtime/runtime.h"
#include "libc/sysv/consts/auxv.h"
struct clockinfo_netbsd {
int32_t hz; // number of clock ticks per second
int32_t tick; // µs per tick
int32_t tickadj; // skew rate for adjtime()
int32_t stathz; // statistics clock frequency
int32_t profhz; // profiling clock frequency
};
static int clk_tck;
static dontinline int __clk_tck_init(void) {
int x;
int cmd[2];
size_t len;
struct clockinfo_netbsd clock;
if (IsWindows()) {
x = HECTONANOSECONDS;
} else if (IsXnu() || IsOpenbsd()) {
x = 100;
} else if (IsFreebsd()) {
x = 128;
} else if (IsNetbsd()) {
cmd[0] = 1; // CTL_KERN
cmd[1] = 12; // KERN_CLOCKRATE
len = sizeof(clock);
if (sys_sysctl(cmd, 2, &clock, &len, NULL, 0) != -1) {
x = clock.hz;
} else {
x = -1;
}
} else {
x = __getauxval(AT_CLKTCK).value;
}
if (x < 1) x = 100;
clk_tck = x;
return x;
}
/**
* Returns system clock ticks per second.
*
* The returned value is memoized. This function is intended to be
* used via the `CLK_TCK` macro wrapper.
*
* The returned value is always greater than zero. It's usually 100
* hertz which means each clock tick is 10 milliseconds long.
*/
int __clk_tck(void) {
if (clk_tck) {
return clk_tck;
} else {
return __clk_tck_init();
}
}