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/* Determine various system internal values, Linux version.
Copyright (C) 1996-2025 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <array_length.h>
#include <assert.h>
#include <ctype.h>
#include <errno.h>
#include <ldsodefs.h>
#include <limits.h>
#include <not-cancel.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <sys/mman.h>
#include <sys/sysinfo.h>
#include <sysdep.h>
static int
__get_nprocs_sched (void)
{
enum
{
max_num_cpus = 32768,
cpu_bits_size = CPU_ALLOC_SIZE (32768)
};
/* This cannot use malloc because it is used on malloc initialization. */
__cpu_mask cpu_bits[cpu_bits_size / sizeof (__cpu_mask)];
int r = INTERNAL_SYSCALL_CALL (sched_getaffinity, 0, cpu_bits_size,
cpu_bits);
if (r > 0)
return CPU_COUNT_S (r, (cpu_set_t*) cpu_bits);
else if (r == -EINVAL)
/* The input buffer is still not enough to store the number of cpus. This
is an arbitrary values assuming such systems should be rare and there
is no offline cpus. */
return max_num_cpus;
/* Some other error. */
return 0;
}
static char *
next_line (int fd, char *const buffer, char **cp, char **re,
char *const buffer_end)
{
char *res = *cp;
char *nl = memchr (*cp, '\n', *re - *cp);
if (nl == NULL)
{
if (*cp != buffer)
{
if (*re == buffer_end)
{
memmove (buffer, *cp, *re - *cp);
*re = buffer + (*re - *cp);
*cp = buffer;
ssize_t n = __read_nocancel (fd, *re, buffer_end - *re);
if (n < 0)
return NULL;
*re += n;
nl = memchr (*cp, '\n', *re - *cp);
while (nl == NULL && *re == buffer_end)
{
/* Truncate too long lines. */
*re = buffer + 3 * (buffer_end - buffer) / 4;
n = __read_nocancel (fd, *re, buffer_end - *re);
if (n < 0)
return NULL;
nl = memchr (*re, '\n', n);
**re = '\n';
*re += n;
}
}
else
nl = memchr (*cp, '\n', *re - *cp);
res = *cp;
}
if (nl == NULL)
nl = *re - 1;
}
*cp = nl + 1;
assert (*cp <= *re);
return res == *re ? NULL : res;
}
static int
get_nproc_stat (void)
{
enum { buffer_size = 1024 };
char buffer[buffer_size];
char *buffer_end = buffer + buffer_size;
char *cp = buffer_end;
char *re = buffer_end;
int result = 0;
const int flags = O_RDONLY | O_CLOEXEC;
int fd = __open_nocancel ("/proc/stat", flags);
if (fd != -1)
{
char *l;
while ((l = next_line (fd, buffer, &cp, &re, buffer_end)) != NULL)
/* The current format of /proc/stat has all the cpu* entries
at the front. We assume here that stays this way. */
if (strncmp (l, "cpu", 3) != 0)
break;
else if (isdigit (l[3]))
++result;
__close_nocancel_nostatus (fd);
}
return result;
}
static int
read_sysfs_file (const char *fname)
{
enum { buffer_size = 1024 };
char buffer[buffer_size];
char *buffer_end = buffer + buffer_size;
char *cp = buffer_end;
char *re = buffer_end;
const int flags = O_RDONLY | O_CLOEXEC;
/* This file contains comma-separated ranges. */
int fd = __open_nocancel (fname, flags);
char *l;
int result = 0;
if (fd != -1)
{
l = next_line (fd, buffer, &cp, &re, buffer_end);
if (l != NULL)
do
{
char *endp;
unsigned long int n = strtoul (l, &endp, 10);
if (l == endp)
{
result = 0;
break;
}
unsigned long int m = n;
if (*endp == '-')
{
l = endp + 1;
m = strtoul (l, &endp, 10);
if (l == endp)
{
result = 0;
break;
}
}
if (m >= n)
result += m - n + 1;
l = endp;
if (l < re && *l == ',')
++l;
}
while (l < re && *l != '\n');
__close_nocancel_nostatus (fd);
}
return result;
}
static int
get_nprocs_fallback (void)
{
int result;
/* Try /proc/stat first. */
result = get_nproc_stat ();
if (result != 0)
return result;
/* Try sched_getaffinity. */
result = __get_nprocs_sched ();
if (result != 0)
return result;
/* We failed to obtain an accurate number. Be conservative: return
the smallest number meaning that this is not a uniprocessor system,
so atomics are needed. */
return 2;
}
int
__get_nprocs (void)
{
int result = read_sysfs_file ("/sys/devices/system/cpu/online");
if (result != 0)
return result;
/* Fall back to /proc/stat and sched_getaffinity. */
return get_nprocs_fallback ();
}
libc_hidden_def (__get_nprocs)
weak_alias (__get_nprocs, get_nprocs)
/* On some architectures it is possible to distinguish between configured
and active cpus. */
int
__get_nprocs_conf (void)
{
int result = read_sysfs_file ("/sys/devices/system/cpu/possible");
if (result != 0)
return result;
/* Fall back to /proc/stat and sched_getaffinity. */
return get_nprocs_fallback ();
}
libc_hidden_def (__get_nprocs_conf)
weak_alias (__get_nprocs_conf, get_nprocs_conf)
/* Compute (num*mem_unit)/pagesize, but avoid overflowing long int.
In practice, mem_unit is never bigger than the page size, so after
the first loop it is 1. [In the kernel, it is initialized to
PAGE_SIZE in mm/page_alloc.c:si_meminfo(), and then in
kernel.sys.c:do_sysinfo() it is set to 1 if unsigned long can
represent all the sizes measured in bytes]. */
static long int
sysinfo_mempages (unsigned long int num, unsigned int mem_unit)
{
unsigned long int ps = __getpagesize ();
while (mem_unit > 1 && ps > 1)
{
mem_unit >>= 1;
ps >>= 1;
}
num *= mem_unit;
while (ps > 1)
{
ps >>= 1;
num >>= 1;
}
return num;
}
/* Return the number of pages of total/available physical memory in
the system. This used to be done by parsing /proc/meminfo, but
that's unnecessarily expensive (and /proc is not always available).
The sysinfo syscall provides the same information, and has been
available at least since kernel 2.3.48. */
long int
__get_phys_pages (void)
{
struct sysinfo info;
__sysinfo (&info);
return sysinfo_mempages (info.totalram, info.mem_unit);
}
libc_hidden_def (__get_phys_pages)
weak_alias (__get_phys_pages, get_phys_pages)
long int
__get_avphys_pages (void)
{
struct sysinfo info;
__sysinfo (&info);
return sysinfo_mempages (info.freeram, info.mem_unit);
}
libc_hidden_def (__get_avphys_pages)
weak_alias (__get_avphys_pages, get_avphys_pages)
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