libgomp/config/linux/proc.c

   1 /* Copyright (C) 2005-2013 Free Software Foundation, Inc.
   2    Contributed by Jakub Jelinek <jakub@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.  */
  27
  28 #ifndef _GNU_SOURCE
  29 #define _GNU_SOURCE 1
  30 #endif
  31 #include "libgomp.h"
  32 #include "proc.h"
  33 #include <stdlib.h>
  34 #include <unistd.h>
  35 #ifdef HAVE_GETLOADAVG
  36 # ifdef HAVE_SYS_LOADAVG_H
  37 #  include <sys/loadavg.h>
  38 # endif
  39 #endif
  40
  41 #ifdef HAVE_PTHREAD_AFFINITY_NP
  42 unsigned long
  43 gomp_cpuset_popcount (cpu_set_t *cpusetp)
  44 {
  45 #ifdef CPU_COUNT
  46   /* glibc 2.6 and above provide a macro for this.  */
  47   return CPU_COUNT (cpusetp);
  48 #else
  49   size_t i;
  50   unsigned long ret = 0;
  51   extern int check[sizeof (cpusetp->__bits[0]) == sizeof (unsigned long int)];
  52
  53   (void) check;
  54   for (i = 0; i < sizeof (*cpusetp) / sizeof (cpusetp->__bits[0]); i++)
  55     {
  56       unsigned long int mask = cpusetp->__bits[i];
  57       if (mask == 0)
  58         continue;
  59       ret += __builtin_popcountl (mask);
  60     }
  61   return ret;
  62 #endif
  63 }
  64 #endif
  65
  66 /* At startup, determine the default number of threads.  It would seem
  67    this should be related to the number of cpus online.  */
  68
  69 void
  70 gomp_init_num_threads (void)
  71 {
  72 #ifdef HAVE_PTHREAD_AFFINITY_NP
  73   cpu_set_t cpuset;
  74
  75   if (pthread_getaffinity_np (pthread_self (), sizeof (cpuset), &cpuset) == 0)
  76     {
  77       /* Count only the CPUs this process can use.  */
  78       gomp_global_icv.nthreads_var = gomp_cpuset_popcount (&cpuset);
  79       if (gomp_global_icv.nthreads_var == 0)
  80         gomp_global_icv.nthreads_var = 1;
  81       return;
  82     }
  83 #endif
  84 #ifdef _SC_NPROCESSORS_ONLN
  85   gomp_global_icv.nthreads_var = sysconf (_SC_NPROCESSORS_ONLN);
  86 #endif
  87 }
  88
  89 static int
  90 get_num_procs (void)
  91 {
  92 #ifdef HAVE_PTHREAD_AFFINITY_NP
  93   cpu_set_t cpuset;
  94
  95   if (gomp_cpu_affinity == NULL)
  96     {
  97       /* Count only the CPUs this process can use.  */
  98       if (pthread_getaffinity_np (pthread_self (), sizeof (cpuset),
  99                                   &cpuset) == 0)
 100         {
 101           int ret = gomp_cpuset_popcount (&cpuset);
 102           return ret != 0 ? ret : 1;
 103         }
 104     }
 105   else
 106     {
 107       /* We can't use pthread_getaffinity_np in this case
 108          (we have changed it ourselves, it binds to just one CPU).
 109          Count instead the number of different CPUs we are
 110          using.  gomp_init_affinity updated gomp_available_cpus to
 111          the number of CPUs in the GOMP_AFFINITY mask that we are
 112          allowed to use though.  */
 113       return gomp_available_cpus;
 114     }
 115 #endif
 116 #ifdef _SC_NPROCESSORS_ONLN
 117   return sysconf (_SC_NPROCESSORS_ONLN);
 118 #else
 119   return gomp_icv (false)->nthreads_var;
 120 #endif
 121 }
 122
 123 /* When OMP_DYNAMIC is set, at thread launch determine the number of
 124    threads we should spawn for this team.  */
 125 /* ??? I have no idea what best practice for this is.  Surely some
 126    function of the number of processors that are *still* online and
 127    the load average.  Here I use the number of processors online
 128    minus the 15 minute load average.  */
 129
 130 unsigned
 131 gomp_dynamic_max_threads (void)
 132 {
 133   unsigned n_onln, loadavg, nthreads_var = gomp_icv (false)->nthreads_var;
 134
 135   n_onln = get_num_procs ();
 136   if (n_onln > nthreads_var)
 137     n_onln = nthreads_var;
 138
 139   loadavg = 0;
 140 #ifdef HAVE_GETLOADAVG
 141   {
 142     double dloadavg[3];
 143     if (getloadavg (dloadavg, 3) == 3)
 144       {
 145         /* Add 0.1 to get a kind of biased rounding.  */
 146         loadavg = dloadavg[2] + 0.1;
 147       }
 148   }
 149 #endif
 150
 151   if (loadavg >= n_onln)
 152     return 1;
 153   else
 154     return n_onln - loadavg;
 155 }
 156
 157 int
 158 omp_get_num_procs (void)
 159 {
 160   return get_num_procs ();
 161 }
 162
 163 ialias (omp_get_num_procs)