glibc/sysdeps/unix/sysv/linux/getsysstats.c

/* Determine various system internal values, Linux version.
   Copyright (C) 1996-2021 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.

   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 <dirent.h>
#include <not-cancel.h>
#include <scratch_buffer.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <sys/sysinfo.h>
#include <sysdep.h>

int
__get_nprocs (void)
{
  struct scratch_buffer set;
  scratch_buffer_init (&set);

  int r;
  while (true)
    {
      /* The possible error are EFAULT for an invalid buffer or ESRCH for
	 invalid pid, none could happen.  */
      r = INTERNAL_SYSCALL_CALL (sched_getaffinity, 0, set.length,
                                 set.data);
      if (r > 0)
        break;

      if (!scratch_buffer_grow (&set))
        /* Default to an SMP system in case we cannot obtain an accurate
           number.  */
        return 2;
    }

  /* The scratch_buffer is aligned to max_align_t.  */
  r = __sched_cpucount (r, (const cpu_set_t *) set.data);

  scratch_buffer_free (&set);

  return r;
}
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)
{
  /* XXX Here will come a test for the new system call.  */

  /* Try to use the sysfs filesystem.  It has actual information about
     online processors.  */
  DIR *dir = __opendir ("/sys/devices/system/cpu");
  if (dir != NULL)
    {
      int count = 0;
      struct dirent64 *d;

      while ((d = __readdir64 (dir)) != NULL)
	/* NB: the sysfs has d_type support.  */
	if (d->d_type == DT_DIR && strncmp (d->d_name, "cpu", 3) == 0)
	  {
	    char *endp;
	    unsigned long int nr = strtoul (d->d_name + 3, &endp, 10);
	    if (nr != ULONG_MAX && endp != d->d_name + 3 && *endp == '\0')
	      ++count;
	  }

      __closedir (dir);

      return count;
    }

  int result = 1;

#ifdef GET_NPROCS_CONF_PARSER
  /* If we haven't found an appropriate entry return 1.  */
  FILE *fp = fopen ("/proc/cpuinfo", "rce");
  if (fp != NULL)
    {
      char buffer[8192];

      /* No threads use this stream.  */
      __fsetlocking (fp, FSETLOCKING_BYCALLER);
      GET_NPROCS_CONF_PARSER (fp, buffer, result);
      fclose (fp);
    }
#else
  result = __get_nprocs ();
#endif

  return result;
}
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)