contrib/gcc-4.7/libgomp/config/bsd/proc.c

   1 /* Copyright (C) 2005, 2006, 2008, 2009 Free Software Foundation, Inc.
   2    Contributed by Richard Henderson <rth@redhat.com>.
   3
   4    This file is part of the GNU OpenMP Library (libgomp).
   5
   6    Libgomp is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3, or (at your option)
   9    any later version.
  10
  11    Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
  12    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  13    FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  14    more details.
  15
  16    Under Section 7 of GPL version 3, you are granted additional
  17    permissions described in the GCC Runtime Library Exception, version
  18    3.1, as published by the Free Software Foundation.
  19
  20    You should have received a copy of the GNU General Public License and
  21    a copy of the GCC Runtime Library Exception along with this program;
  22    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23    <http://www.gnu.org/licenses/>.  */
  24
  25 /* This file contains system specific routines related to counting
  26    online processors and dynamic load balancing.  It is expected that
  27    a system may well want to write special versions of each of these.
  28
  29    The following implementation uses a mix of POSIX and BSD routines.  */
  30
  31 #include "libgomp.h"
  32 #include <unistd.h>
  33 #include <stdlib.h>
  34 #ifdef HAVE_GETLOADAVG
  35 # ifdef HAVE_SYS_LOADAVG_H
  36 #  include <sys/loadavg.h>
  37 # endif
  38 #endif
  39 #ifdef HAVE_SYS_SYSCTL_H
  40 # include <sys/sysctl.h>
  41 #endif
  42
  43 static int
  44 get_num_procs (void)
  45 {
  46 #ifdef _SC_NPROCESSORS_ONLN
  47   return sysconf (_SC_NPROCESSORS_ONLN);
  48 #elif defined HW_NCPU
  49   int ncpus = 1;
  50   size_t len = sizeof(ncpus);
  51   sysctl((int[2]) {CTL_HW, HW_NCPU}, 2, &ncpus, &len, NULL, 0);
  52   return ncpus;
  53 #else
  54   return 0;
  55 #endif
  56 }
  57
  58 /* At startup, determine the default number of threads.  It would seem
  59    this should be related to the number of cpus online.  */
  60
  61 void
  62 gomp_init_num_threads (void)
  63 {
  64   int ncpus = get_num_procs ();
  65
  66   if (ncpus > 0)
  67     gomp_global_icv.nthreads_var = ncpus;
  68 }
  69
  70 /* When OMP_DYNAMIC is set, at thread launch determine the number of
  71    threads we should spawn for this team.  */
  72 /* ??? I have no idea what best practice for this is.  Surely some
  73    function of the number of processors that are *still* online and
  74    the load average.  Here I use the number of processors online
  75    minus the 15 minute load average.  */
  76
  77 unsigned
  78 gomp_dynamic_max_threads (void)
  79 {
  80   unsigned n_onln, loadavg;
  81   unsigned nthreads_var = gomp_icv (false)->nthreads_var;
  82
  83   n_onln = get_num_procs ();
  84   if (!n_onln || n_onln > nthreads_var)
  85     n_onln = nthreads_var;
  86
  87   loadavg = 0;
  88 #ifdef HAVE_GETLOADAVG
  89   {
  90     double dloadavg[3];
  91     if (getloadavg (dloadavg, 3) == 3)
  92       {
  93         /* Add 0.1 to get a kind of biased rounding.  */
  94         loadavg = dloadavg[2] + 0.1;
  95       }
  96   }
  97 #endif
  98
  99   if (loadavg >= n_onln)
 100     return 1;
 101   else
 102     return n_onln - loadavg;
 103 }
 104
 105 int
 106 omp_get_num_procs (void)
 107 {
 108   int ncpus = get_num_procs ();
 109   if (ncpus <= 0)
 110     ncpus = gomp_icv (false)->nthreads_var;
 111   return ncpus;
 112 }
 113
 114 ialias (omp_get_num_procs)