cubefs

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// Copyright 2018 Tobias Klauser. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package sysconf
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import (
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	"bufio"
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	"io/ioutil"
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	"os"
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	"runtime"
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	"strconv"
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	"strings"
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	"github.com/tklauser/numcpus"
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	"golang.org/x/sys/unix"
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)
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const (
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	// CLK_TCK is a constant on Linux for all architectures except alpha and ia64.
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	// See e.g.
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	// https://git.musl-libc.org/cgit/musl/tree/src/conf/sysconf.c#n30
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	// https://github.com/containerd/cgroups/pull/12
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	// https://lore.kernel.org/lkml/agtlq6$iht$1@penguin.transmeta.com/
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	_SYSTEM_CLK_TCK = 100
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)
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func readProcFsInt64(path string, fallback int64) int64 {
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	data, err := ioutil.ReadFile(path)
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	if err != nil {
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		return fallback
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	}
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	i, err := strconv.ParseInt(string(data[:len(data)-1]), 0, 64)
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	if err != nil {
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		return fallback
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	}
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	return i
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}
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// getMemPages computes mem*unit/os.Getpagesize(), but avoids overflowing int64.
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func getMemPages(mem uint64, unit uint32) int64 {
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	pageSize := os.Getpagesize()
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	for unit > 1 && pageSize > 1 {
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		unit >>= 1
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		pageSize >>= 1
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	}
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	mem *= uint64(unit)
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	for pageSize > 1 {
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		pageSize >>= 1
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		mem >>= 1
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	}
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	return int64(mem)
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}
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func getPhysPages() int64 {
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	var si unix.Sysinfo_t
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	err := unix.Sysinfo(&si)
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	if err != nil {
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		return int64(0)
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	}
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	return getMemPages(uint64(si.Totalram), si.Unit)
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}
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func getAvPhysPages() int64 {
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	var si unix.Sysinfo_t
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	err := unix.Sysinfo(&si)
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	if err != nil {
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		return int64(0)
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	}
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	return getMemPages(uint64(si.Freeram), si.Unit)
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}
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func getNprocsSysfs() (int64, error) {
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	n, err := numcpus.GetOnline()
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	return int64(n), err
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}
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func getNprocsProcStat() (int64, error) {
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	f, err := os.Open("/proc/stat")
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	if err != nil {
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		return -1, err
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	}
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	defer f.Close()
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	count := int64(0)
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	s := bufio.NewScanner(f)
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	for s.Scan() {
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		if line := strings.TrimSpace(s.Text()); strings.HasPrefix(line, "cpu") {
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			l := strings.SplitN(line, " ", 2)
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			_, err := strconv.ParseInt(l[0][3:], 10, 64)
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			if err == nil {
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				count++
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			}
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		} else {
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			// The current format of /proc/stat has all the
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			// cpu* lines at the beginning. Assume this
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			// stays this way.
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			break
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		}
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	}
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	return count, nil
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}
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func getNprocs() int64 {
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	count, err := getNprocsSysfs()
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	if err == nil {
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		return count
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	}
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	count, err = getNprocsProcStat()
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	if err == nil {
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		return count
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	}
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	// default to the value determined at runtime startup if all else fails
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	return int64(runtime.NumCPU())
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}
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func getNprocsConf() int64 {
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	count, err := numcpus.GetConfigured()
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	if err == nil {
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		return int64(count)
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	}
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	// TODO(tk): fall back to reading /proc/cpuinfo on legacy systems
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	// without sysfs?
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	return getNprocs()
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}
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func hasClock(clockid int32) bool {
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	var res unix.Timespec
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	if err := unix.ClockGetres(clockid, &res); err != nil {
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		return false
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	}
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	return true
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}
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func max(a, b int64) int64 {
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	if a > b {
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		return a
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	}
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	return b
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}
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func sysconf(name int) (int64, error) {
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	switch name {
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	case SC_AIO_LISTIO_MAX:
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		return -1, nil
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	case SC_AIO_MAX:
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		return -1, nil
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	case SC_AIO_PRIO_DELTA_MAX:
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		return _AIO_PRIO_DELTA_MAX, nil
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	case SC_ARG_MAX:
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		argMax := int64(_POSIX_ARG_MAX)
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		var rlim unix.Rlimit
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		if err := unix.Getrlimit(unix.RLIMIT_STACK, &rlim); err == nil {
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			argMax = max(argMax, int64(rlim.Cur/4))
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		}
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		return argMax, nil
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	case SC_ATEXIT_MAX:
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		return _INT_MAX, nil
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	case SC_CHILD_MAX:
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		childMax := int64(-1)
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		var rlim unix.Rlimit
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		if err := unix.Getrlimit(unix.RLIMIT_NPROC, &rlim); err == nil && rlim.Cur != unix.RLIM_INFINITY {
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			childMax = int64(rlim.Cur)
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		}
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		return childMax, nil
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	case SC_CLK_TCK:
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		return _SYSTEM_CLK_TCK, nil
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	case SC_DELAYTIMER_MAX:
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		return _DELAYTIMER_MAX, nil
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	case SC_GETGR_R_SIZE_MAX:
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		return _NSS_BUFLEN_GROUP, nil
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	case SC_GETPW_R_SIZE_MAX:
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		return _NSS_BUFLEN_PASSWD, nil
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	case SC_MQ_OPEN_MAX:
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		return -1, nil
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	case SC_MQ_PRIO_MAX:
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		return _MQ_PRIO_MAX, nil
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	case SC_NGROUPS_MAX:
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		return readProcFsInt64("/proc/sys/kernel/ngroups_max", _NGROUPS_MAX), nil
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	case SC_OPEN_MAX:
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		openMax := int64(_OPEN_MAX)
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		var rlim unix.Rlimit
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		if err := unix.Getrlimit(unix.RLIMIT_NOFILE, &rlim); err == nil {
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			openMax = int64(rlim.Cur)
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		}
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		return openMax, nil
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	case SC_RTSIG_MAX:
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		return _RTSIG_MAX, nil
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	case SC_SEM_NSEMS_MAX:
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		return -1, nil
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	case SC_SEM_VALUE_MAX:
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		return _SEM_VALUE_MAX, nil
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	case SC_SIGQUEUE_MAX:
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		var rlim unix.Rlimit
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		if err := unix.Getrlimit(unix.RLIMIT_SIGPENDING, &rlim); err == nil {
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			return int64(rlim.Cur), nil
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		}
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		return readProcFsInt64("/proc/sys/kernel/rtsig-max", _POSIX_SIGQUEUE_MAX), nil
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	case SC_STREAM_MAX:
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		return _STREAM_MAX, nil
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	case SC_THREAD_DESTRUCTOR_ITERATIONS:
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		return _POSIX_THREAD_DESTRUCTOR_ITERATIONS, nil
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	case SC_THREAD_KEYS_MAX:
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		return _PTHREAD_KEYS_MAX, nil
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	case SC_THREAD_PRIO_INHERIT:
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		return _POSIX_THREAD_PRIO_INHERIT, nil
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	case SC_THREAD_PRIO_PROTECT:
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		return _POSIX_THREAD_PRIO_PROTECT, nil
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	case SC_THREAD_STACK_MIN:
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		return _PTHREAD_STACK_MIN, nil
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	case SC_THREAD_THREADS_MAX:
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		return -1, nil
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	case SC_TIMER_MAX:
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		return -1, nil
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	case SC_TTY_NAME_MAX:
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		return _TTY_NAME_MAX, nil
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	case SC_TZNAME_MAX:
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		return -1, nil
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	case SC_CPUTIME:
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		if hasClock(unix.CLOCK_PROCESS_CPUTIME_ID) {
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			return _POSIX_VERSION, nil
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		}
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		return -1, nil
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	case SC_MONOTONIC_CLOCK:
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		if hasClock(unix.CLOCK_MONOTONIC) {
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			return _POSIX_VERSION, nil
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		}
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		return -1, nil
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	case SC_SAVED_IDS:
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		return _POSIX_SAVED_IDS, nil
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	case SC_SPAWN:
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		return _POSIX_SPAWN, nil
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	case SC_SPIN_LOCKS:
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		return _POSIX_SPIN_LOCKS, nil
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	case SC_SPORADIC_SERVER:
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		return _POSIX_SPORADIC_SERVER, nil
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	case SC_SYNCHRONIZED_IO:
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		return _POSIX_SYNCHRONIZED_IO, nil
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	case SC_THREAD_ATTR_STACKADDR:
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		return _POSIX_THREAD_ATTR_STACKADDR, nil
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	case SC_THREAD_ATTR_STACKSIZE:
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		return _POSIX_THREAD_ATTR_STACKSIZE, nil
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	case SC_THREAD_CPUTIME:
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		if hasClock(unix.CLOCK_THREAD_CPUTIME_ID) {
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			return _POSIX_VERSION, nil
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		}
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		return -1, nil
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	case SC_THREAD_PRIORITY_SCHEDULING:
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		return _POSIX_THREAD_PRIORITY_SCHEDULING, nil
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	case SC_THREAD_PROCESS_SHARED:
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		return _POSIX_THREAD_PROCESS_SHARED, nil
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	case SC_THREAD_SAFE_FUNCTIONS:
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		return _POSIX_THREAD_SAFE_FUNCTIONS, nil
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	case SC_THREAD_SPORADIC_SERVER:
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		return _POSIX_THREAD_SPORADIC_SERVER, nil
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	case SC_TRACE:
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		return _POSIX_TRACE, nil
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	case SC_TRACE_EVENT_FILTER:
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		return _POSIX_TRACE_EVENT_FILTER, nil
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	case SC_TRACE_EVENT_NAME_MAX:
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		return -1, nil
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	case SC_TRACE_INHERIT:
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		return _POSIX_TRACE_INHERIT, nil
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	case SC_TRACE_LOG:
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		return _POSIX_TRACE_LOG, nil
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	case SC_TRACE_NAME_MAX:
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		return -1, nil
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	case SC_TRACE_SYS_MAX:
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		return -1, nil
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	case SC_TRACE_USER_EVENT_MAX:
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		return -1, nil
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	case SC_TYPED_MEMORY_OBJECTS:
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		return _POSIX_TYPED_MEMORY_OBJECTS, nil
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	case SC_V7_ILP32_OFF32:
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		return _POSIX_V7_ILP32_OFF32, nil
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	case SC_V7_ILP32_OFFBIG:
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		return _POSIX_V7_ILP32_OFFBIG, nil
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	case SC_V7_LP64_OFF64:
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		return _POSIX_V7_LP64_OFF64, nil
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	case SC_V7_LPBIG_OFFBIG:
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		return _POSIX_V7_LPBIG_OFFBIG, nil
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	case SC_V6_ILP32_OFF32:
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		return _POSIX_V6_ILP32_OFF32, nil
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	case SC_V6_ILP32_OFFBIG:
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		return _POSIX_V6_ILP32_OFFBIG, nil
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	case SC_V6_LP64_OFF64:
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		return _POSIX_V6_LP64_OFF64, nil
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	case SC_V6_LPBIG_OFFBIG:
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		return _POSIX_V6_LPBIG_OFFBIG, nil
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	case SC_2_C_VERSION:
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		return _POSIX2_C_VERSION, nil
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	case SC_2_CHAR_TERM:
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		return _POSIX2_CHAR_TERM, nil
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	case SC_2_PBS,
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		SC_2_PBS_ACCOUNTING,
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		SC_2_PBS_CHECKPOINT,
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		SC_2_PBS_LOCATE,
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		SC_2_PBS_MESSAGE,
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		SC_2_PBS_TRACK:
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		return -1, nil
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	case SC_2_UPE:
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		return -1, nil
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	case SC_XOPEN_CRYPT:
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		// removed in glibc 2.28
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		return -1, nil
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	case SC_XOPEN_ENH_I18N:
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		return _XOPEN_ENH_I18N, nil
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	case SC_XOPEN_REALTIME:
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		return _XOPEN_REALTIME, nil
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	case SC_XOPEN_REALTIME_THREADS:
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		return _XOPEN_REALTIME_THREADS, nil
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	case SC_XOPEN_SHM:
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		return _XOPEN_SHM, nil
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	case SC_XOPEN_STREAMS:
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		return -1, nil
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	case SC_XOPEN_UNIX:
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		return _XOPEN_UNIX, nil
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	case SC_XOPEN_VERSION:
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		return _XOPEN_VERSION, nil
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	case SC_XOPEN_XCU_VERSION:
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		return _XOPEN_XCU_VERSION, nil
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	case SC_PHYS_PAGES:
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		return getPhysPages(), nil
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	case SC_AVPHYS_PAGES:
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		return getAvPhysPages(), nil
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	case SC_NPROCESSORS_CONF:
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		return getNprocsConf(), nil
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	case SC_NPROCESSORS_ONLN:
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		return getNprocs(), nil
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	case SC_UIO_MAXIOV: // same as _SC_IOV_MAX
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		return _UIO_MAXIOV, nil
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	}
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	return sysconfGeneric(name)
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}
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