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1 /* Copyright (C) 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
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2 Contributed by Jakub Jelinek <jakub@redhat.com>.
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3
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4 This file is part of the GNU OpenMP Library (libgomp).
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5
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6 Libgomp is free software; you can redistribute it and/or modify it
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7 under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 3, or (at your option)
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9 any later version.
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10
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11 Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
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12 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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13 FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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14 more details.
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15
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16 Under Section 7 of GPL version 3, you are granted additional
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17 permissions described in the GCC Runtime Library Exception, version
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18 3.1, as published by the Free Software Foundation.
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19
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20 You should have received a copy of the GNU General Public License and
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21 a copy of the GCC Runtime Library Exception along with this program;
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22 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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23 <http://www.gnu.org/licenses/>. */
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24
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25 /* This file contains system specific routines related to counting
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26 online processors and dynamic load balancing. */
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27
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28 #ifndef _GNU_SOURCE
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29 #define _GNU_SOURCE 1
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30 #endif
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31 #include "libgomp.h"
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32 #include <sched.h>
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33 #include <stdlib.h>
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34 #include <unistd.h>
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35 #ifdef HAVE_GETLOADAVG
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36 # ifdef HAVE_SYS_LOADAVG_H
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37 # include <sys/loadavg.h>
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38 # endif
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39 #endif
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40
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41 #ifdef HAVE_PTHREAD_AFFINITY_NP
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42 static unsigned long
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43 cpuset_popcount (cpu_set_t *cpusetp)
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44 {
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45 #ifdef CPU_COUNT
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46 /* glibc 2.6 and above provide a macro for this. */
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47 return CPU_COUNT (cpusetp);
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48 #else
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49 size_t i;
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50 unsigned long ret = 0;
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51 extern int check[sizeof (cpusetp->__bits[0]) == sizeof (unsigned long int)];
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52
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53 (void) check;
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54 for (i = 0; i < sizeof (*cpusetp) / sizeof (cpusetp->__bits[0]); i++)
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55 {
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56 unsigned long int mask = cpusetp->__bits[i];
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57 if (mask == 0)
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58 continue;
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59 ret += __builtin_popcountl (mask);
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60 }
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61 return ret;
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62 #endif
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63 }
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64 #endif
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65
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66 /* At startup, determine the default number of threads. It would seem
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67 this should be related to the number of cpus online. */
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68
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69 void
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70 gomp_init_num_threads (void)
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71 {
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72 #ifdef HAVE_PTHREAD_AFFINITY_NP
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73 cpu_set_t cpuset;
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74
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75 if (pthread_getaffinity_np (pthread_self (), sizeof (cpuset), &cpuset) == 0)
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76 {
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77 /* Count only the CPUs this process can use. */
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78 gomp_global_icv.nthreads_var = cpuset_popcount (&cpuset);
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79 if (gomp_global_icv.nthreads_var == 0)
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80 gomp_global_icv.nthreads_var = 1;
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81 return;
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82 }
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83 #endif
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84 #ifdef _SC_NPROCESSORS_ONLN
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85 gomp_global_icv.nthreads_var = sysconf (_SC_NPROCESSORS_ONLN);
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86 #endif
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87 }
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88
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89 static int
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90 get_num_procs (void)
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91 {
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92 #ifdef HAVE_PTHREAD_AFFINITY_NP
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93 cpu_set_t cpuset;
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94
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95 if (gomp_cpu_affinity == NULL)
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96 {
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97 /* Count only the CPUs this process can use. */
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98 if (pthread_getaffinity_np (pthread_self (), sizeof (cpuset),
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99 &cpuset) == 0)
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100 {
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101 int ret = cpuset_popcount (&cpuset);
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102 return ret != 0 ? ret : 1;
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103 }
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104 }
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105 else
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106 {
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107 size_t idx;
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108 static int affinity_cpus;
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109
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110 /* We can't use pthread_getaffinity_np in this case
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111 (we have changed it ourselves, it binds to just one CPU).
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112 Count instead the number of different CPUs we are
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113 using. */
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114 CPU_ZERO (&cpuset);
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115 if (affinity_cpus == 0)
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116 {
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117 int cpus = 0;
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118 for (idx = 0; idx < gomp_cpu_affinity_len; idx++)
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119 if (! CPU_ISSET (gomp_cpu_affinity[idx], &cpuset))
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120 {
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121 cpus++;
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122 CPU_SET (gomp_cpu_affinity[idx], &cpuset);
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123 }
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124 affinity_cpus = cpus;
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125 }
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126 return affinity_cpus;
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127 }
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128 #endif
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129 #ifdef _SC_NPROCESSORS_ONLN
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130 return sysconf (_SC_NPROCESSORS_ONLN);
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131 #else
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132 return gomp_icv (false)->nthreads_var;
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133 #endif
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134 }
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135
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136 /* When OMP_DYNAMIC is set, at thread launch determine the number of
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137 threads we should spawn for this team. */
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138 /* ??? I have no idea what best practice for this is. Surely some
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139 function of the number of processors that are *still* online and
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140 the load average. Here I use the number of processors online
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141 minus the 15 minute load average. */
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142
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143 unsigned
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144 gomp_dynamic_max_threads (void)
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145 {
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146 unsigned n_onln, loadavg, nthreads_var = gomp_icv (false)->nthreads_var;
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147
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148 n_onln = get_num_procs ();
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149 if (n_onln > nthreads_var)
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150 n_onln = nthreads_var;
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151
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152 loadavg = 0;
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153 #ifdef HAVE_GETLOADAVG
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154 {
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155 double dloadavg[3];
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156 if (getloadavg (dloadavg, 3) == 3)
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157 {
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158 /* Add 0.1 to get a kind of biased rounding. */
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159 loadavg = dloadavg[2] + 0.1;
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160 }
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161 }
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162 #endif
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163
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164 if (loadavg >= n_onln)
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165 return 1;
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166 else
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167 return n_onln - loadavg;
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168 }
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169
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170 int
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171 omp_get_num_procs (void)
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172 {
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173 return get_num_procs ();
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174 }
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175
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176 ialias (omp_get_num_procs)
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