mariadb/mysys/my_getncpus.c

/*
   Copyright (c) 2006, 2010, Oracle and/or its affiliates

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335  USA */

/* get the number of (online) CPUs */

#include "mysys_priv.h"
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#if defined(__FreeBSD__) && defined(HAVE_PTHREAD_GETAFFINITY_NP)
#include <pthread_np.h>
#include <sys/cpuset.h>
#endif

static int ncpus=0;

int my_getncpus(void)
{
  if (!ncpus)
  {
    /*
      First attempt to get the total number of available cores. sysconf is
      the fallback, but it can return a larger number. It will return the
      total number of cores, not the ones available to the process - as
      configured via core affinity.
    */
#if (defined(__linux__) || defined(__FreeBSD__)) && defined(HAVE_PTHREAD_GETAFFINITY_NP)
#ifdef __linux__
    cpu_set_t set;
#else
    cpuset_t set;
#endif
    if (pthread_getaffinity_np(pthread_self(), sizeof(set), &set) == 0)
    {
#ifdef CPU_COUNT
      /* CPU_COUNT was introduced with glibc 2.6. */
      ncpus= CPU_COUNT(&set);
#else
      /* Implementation for platforms with glibc < 2.6 */
      size_t i;

      for (i= 0; i < CPU_SETSIZE; i++)
        if (CPU_ISSET(i, &set))
          ncpus++;
#endif
      return ncpus;
    }
#endif /* (__linux__ || __FreeBSD__) && HAVE_PTHREAD_GETAFFINITY_NP */

#ifdef _SC_NPROCESSORS_ONLN
    ncpus= sysconf(_SC_NPROCESSORS_ONLN);
#elif defined(_WIN32)
    SYSTEM_INFO sysinfo;

    /*
      We are not calling GetNativeSystemInfo here because (1) we
      don't believe that they return different values for number
      of processors and (2) if WOW64 limits processors for Win32
      then we don't want to try to override that.
    */
    GetSystemInfo(&sysinfo);

    ncpus= sysinfo.dwNumberOfProcessors;
#else
    /* Unknown so play safe: assume SMP and forbid uniprocessor build */
    ncpus= 2;
#endif
  }

  return ncpus;
}