gomp-20050608-branch/libgomp/config/posix/proc.c

   1 /* Copyright (C) 2005, 2006 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 Lesser General Public License as published by
   8    the Free Software Foundation; either version 2.1 of the License, or
   9    (at your option) 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 Lesser General Public License for
  14    more details.
  15
  16    You should have received a copy of the GNU Lesser General Public License
  17    along with libgomp; see the file COPYING.LIB.  If not, write to the
  18    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  19    MA 02110-1301, USA.  */
  20
  21 /* As a special exception, if you link this library with other files, some
  22    of which are compiled with GCC, to produce an executable, this library
  23    does not by itself cause the resulting executable to be covered by the
  24    GNU General Public License.  This exception does not however invalidate
  25    any other reasons why the executable file might be covered by the GNU
  26    General Public License.  */
  27
  28 /* This file contains system specific routines related to counting
  29    online processors and dynamic load balancing.  It is expected that
  30    a system may well want to write special versions of each of these.
  31
  32    The following implementation uses a mix of POSIX and BSD routines.  */
  33
  34 #include "libgomp.h"
  35 #include <unistd.h>
  36 #include <stdlib.h>
  37 #ifdef HAVE_GETLOADAVG
  38 # ifdef HAVE_SYS_LOADAVG_H
  39 #  include <sys/loadavg.h>
  40 # endif
  41 #endif
  42
  43
  44 /* At startup, determine the default number of threads.  It would seem
  45    this should be related to the number of cpus online.  */
  46
  47 void
  48 gomp_init_num_threads (void)
  49 {
  50 #ifdef _SC_NPROCESSORS_ONLN
  51   gomp_nthreads_var = sysconf (_SC_NPROCESSORS_ONLN);
  52 #endif
  53 }
  54
  55 /* When OMP_DYNAMIC is set, at thread launch determine the number of
  56    threads we should spawn for this team.  */
  57 /* ??? I have no idea what best practice for this is.  Surely some
  58    function of the number of processors that are *still* online and
  59    the load average.  Here I use the number of processors online
  60    minus the 15 minute load average.  */
  61
  62 unsigned
  63 gomp_dynamic_max_threads (void)
  64 {
  65   unsigned n_onln, loadavg;
  66
  67 #ifdef _SC_NPROCESSORS_ONLN
  68   n_onln = sysconf (_SC_NPROCESSORS_ONLN);
  69   if (n_onln > gomp_nthreads_var)
  70     n_onln = gomp_nthreads_var;
  71 #else
  72   n_onln = gomp_nthreads_var;
  73 #endif
  74
  75   loadavg = 0;
  76 #ifdef HAVE_GETLOADAVG
  77   {
  78     double dloadavg[3];
  79     if (getloadavg (dloadavg, 3) == 3)
  80       {
  81         /* Add 0.1 to get a kind of biased rounding.  */
  82         loadavg = dloadavg[2] + 0.1;
  83       }
  84   }
  85 #endif
  86
  87   if (loadavg >= n_onln)
  88     return 1;
  89   else
  90     return n_onln - loadavg;
  91 }
  92
  93 int
  94 omp_get_num_procs (void)
  95 {
  96 #ifdef _SC_NPROCESSORS_ONLN
  97   return sysconf (_SC_NPROCESSORS_ONLN);
  98 #else
  99   return gomp_nthreads_var;
 100 #endif
 101 }
 102
 103 ialias (omp_get_num_procs)