[PATCH 1/2] Linux: implement getloadavg(3) using sysinfo(2)

Cristian Rodríguez crrodriguez@opensuse.org
Thu Aug 12 18:51:41 GMT 2021


ping

On Fri, Aug 6, 2021 at 3:18 PM Cristian Rodríguez
<crrodriguez@opensuse.org> wrote:
>
> Signed-off-by: Cristian Rodríguez <crrodriguez@opensuse.org>
> ---
>  sysdeps/unix/sysv/linux/getloadavg.c | 50 ++++++++--------------------
>  1 file changed, 14 insertions(+), 36 deletions(-)
>
> diff --git a/sysdeps/unix/sysv/linux/getloadavg.c b/sysdeps/unix/sysv/linux/getloadavg.c
> index e50cc396e7..3ea7fd02b7 100644
> --- a/sysdeps/unix/sysv/linux/getloadavg.c
> +++ b/sysdeps/unix/sysv/linux/getloadavg.c
> @@ -1,4 +1,4 @@
> -/* Get system load averages.  Linux (/proc/loadavg) version.
> +/* Get system load averages.  Linux version.
>     Copyright (C) 1999-2021 Free Software Foundation, Inc.
>     This file is part of the GNU C Library.
>
> @@ -16,53 +16,31 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>
> -#include <errno.h>
> -#include <fcntl.h>
> -#include <locale.h>
> -#include <stdlib.h>
> -#include <unistd.h>
> -#include <not-cancel.h>
> +#include <array_length.h>
> +#include <sys/param.h>
> +#include <sys/sysinfo.h>
>
>  /* Put the 1 minute, 5 minute and 15 minute load averages
>     into the first NELEM elements of LOADAVG.
>     Return the number written (never more than 3, but may be less than NELEM),
>     or -1 if an error occurred.  */
>
> +#define CLAMP(v, lo, hi) MIN (MAX (v, lo), hi)
> +
> +#define SYSINFO_LOADS_SCALE (1 << SI_LOAD_SHIFT)
> +
>  int
>  getloadavg (double loadavg[], int nelem)
>  {
> -  int fd;
> +  struct sysinfo info = {};
>
> -  fd = __open_nocancel ("/proc/loadavg", O_RDONLY);
> -  if (fd < 0)
> +  if (__sysinfo (&info) != 0)
>      return -1;
> -  else
> -    {
> -      char buf[65], *p;
> -      ssize_t nread;
> -      int i;
>
> -      nread = __read_nocancel (fd, buf, sizeof buf - 1);
> -      __close_nocancel_nostatus (fd);
> -      if (nread <= 0)
> -       return -1;
> -      buf[nread - 1] = '\0';
> +  nelem = CLAMP (nelem, 0, (int)array_length (info.loads));
>
> -      if (nelem > 3)
> -       nelem = 3;
> -      p = buf;
> -      for (i = 0; i < nelem; ++i)
> -       {
> -         char *endp;
> -         loadavg[i] = __strtod_l (p, &endp, _nl_C_locobj_ptr);
> -         if (endp == p)
> -           /* This should not happen.  The format of /proc/loadavg
> -              must have changed.  Don't return with what we have,
> -              signal an error.  */
> -           return -1;
> -         p = endp;
> -       }
> +  for (int i = 0; i < nelem; i++)
> +    loadavg[i] = (double)info.loads[i] / SYSINFO_LOADS_SCALE;
>
> -      return i;
> -    }
> +  return nelem;
>  }
> --
> 2.32.0


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