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From: "David Luyer" <david@luyer.net>
To: "'Alan Cox'" <alan@lxorguk.ukuu.org.uk>
Cc: <linux-kernel@vger.kernel.org>
Subject: RE: Linux 2.4.19ac3rc3 on IBM x330/x340 SMP - "ps" time skew
Date: Wed, 31 Jul 2002 23:18:10 +1000
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> On Wed, 2002-07-31 at 13:59, David Luyer wrote:
> >   printf("%d\n", sysconf(_SC_NPROCESSORS_CONF));
> > }
> > luyer@praxis8:~$ ./cpus
> > 4
> > luyer@praxis8:~$ grep 'processor        ' /proc/cpuinfo
> > processor       : 0
> > processor       : 1
> 
> In which case I suggest you file a glibc bug. sysconf looks 
> at the /proc stuff as I understand it

Great, got it, thanks: sysconf(_SC_NPROCESSORS_CONF) parses
/proc/cpuinfo
using a simple parser:

#ifndef GET_NPROCS_PARSER
# define GET_NPROCS_PARSER(FP, BUFFER, RESULT)
\
  do
\
    {
\
      (RESULT) = 0;
\
      /* Read all lines and count the lines starting with the string
\
         "processor".  We don't have to fear extremely long lines since
\
         the kernel will not generate them.  8192 bytes are really
\
         enough.  */
\
      while (fgets_unlocked (BUFFER, sizeof (BUFFER), FP) != NULL)
\
        if (strncmp (BUFFER, "processor", 9) == 0)
\
          ++(RESULT);
\
    }
\
  while (0)
#endif

It's being tricked by this:

luyer@praxis8:~$ cat /proc/cpuinfo | grep '^processor'
processor       : 0
processor id    : 0
processor       : 1
processor id    : 0

The "processor id" line, only present with SMP enabled, is being counted
as a processor.

David.

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