1 /* Copyright (C) 2005-2022 Free Software Foundation, Inc. 2 Contributed by Jakub Jelinek <jakub (at) redhat.com>. 3 4 This file is part of the GNU Offloading and Multi Processing Library 5 (libgomp). 6 7 Libgomp is free software; you can redistribute it and/or modify it 8 under the terms of the GNU General Public License as published by 9 the Free Software Foundation; either version 3, or (at your option) 10 any later version. 11 12 Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY 13 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS 14 FOR A PARTICULAR PURPOSE. See the GNU General Public License for 15 more details. 16 17 Under Section 7 of GPL version 3, you are granted additional 18 permissions described in the GCC Runtime Library Exception, version 19 3.1, as published by the Free Software Foundation. 20 21 You should have received a copy of the GNU General Public License and 22 a copy of the GCC Runtime Library Exception along with this program; 23 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 24 <http://www.gnu.org/licenses/>. */ 25 26 /* This file contains system specific routines related to counting 27 online processors and dynamic load balancing. */ 28 29 #ifndef _GNU_SOURCE 30 #define _GNU_SOURCE 1 31 #endif 32 #include "libgomp.h" 33 #include "proc.h" 34 #include <errno.h> 35 #include <stdlib.h> 36 #include <unistd.h> 37 #ifdef HAVE_GETLOADAVG 38 # ifdef HAVE_SYS_LOADAVG_H 39 # include <sys/loadavg.h> 40 # endif 41 #endif 42 43 #ifdef HAVE_PTHREAD_AFFINITY_NP 44 unsigned long gomp_cpuset_size; 45 static unsigned long gomp_get_cpuset_size; 46 cpu_set_t *gomp_cpusetp; 47 48 unsigned long 49 gomp_cpuset_popcount (unsigned long cpusetsize, cpu_set_t *cpusetp) 50 { 51 #ifdef CPU_COUNT_S 52 /* glibc 2.7 and above provide a macro for this. */ 53 return CPU_COUNT_S (cpusetsize, cpusetp); 54 #else 55 #ifdef CPU_COUNT 56 if (cpusetsize == sizeof (cpu_set_t)) 57 /* glibc 2.6 and above provide a macro for this. */ 58 return CPU_COUNT (cpusetp); 59 #endif 60 size_t i; 61 unsigned long ret = 0; 62 extern int check[sizeof (cpusetp->__bits[0]) == sizeof (unsigned long int) 63 ? 1 : -1] __attribute__((unused)); 64 65 for (i = 0; i < cpusetsize / sizeof (cpusetp->__bits[0]); i++) 66 { 67 unsigned long int mask = cpusetp->__bits[i]; 68 if (mask == 0) 69 continue; 70 ret += __builtin_popcountl (mask); 71 } 72 return ret; 73 #endif 74 } 75 #endif 76 77 /* At startup, determine the default number of threads. It would seem 78 this should be related to the number of cpus online. */ 79 80 void 81 gomp_init_num_threads (void) 82 { 83 #ifdef HAVE_PTHREAD_AFFINITY_NP 84 #if defined (_SC_NPROCESSORS_CONF) && defined (CPU_ALLOC_SIZE) 85 gomp_cpuset_size = sysconf (_SC_NPROCESSORS_CONF); 86 gomp_cpuset_size = CPU_ALLOC_SIZE (gomp_cpuset_size); 87 #else 88 gomp_cpuset_size = sizeof (cpu_set_t); 89 #endif 90 91 gomp_cpusetp = (cpu_set_t *) gomp_malloc (gomp_cpuset_size); 92 do 93 { 94 int ret = pthread_getaffinity_np (pthread_self (), gomp_cpuset_size, 95 gomp_cpusetp); 96 if (ret == 0) 97 { 98 /* Count only the CPUs this process can use. */ 99 gomp_global_icv.nthreads_var 100 = gomp_cpuset_popcount (gomp_cpuset_size, gomp_cpusetp); 101 if (gomp_global_icv.nthreads_var == 0) 102 break; 103 gomp_get_cpuset_size = gomp_cpuset_size; 104 #ifdef CPU_ALLOC_SIZE 105 unsigned long i; 106 for (i = gomp_cpuset_size * 8; i; i--) 107 if (CPU_ISSET_S (i - 1, gomp_cpuset_size, gomp_cpusetp)) 108 break; 109 gomp_cpuset_size = CPU_ALLOC_SIZE (i); 110 #endif 111 return; 112 } 113 if (ret != EINVAL) 114 break; 115 #ifdef CPU_ALLOC_SIZE 116 if (gomp_cpuset_size < sizeof (cpu_set_t)) 117 gomp_cpuset_size = sizeof (cpu_set_t); 118 else 119 gomp_cpuset_size = gomp_cpuset_size * 2; 120 if (gomp_cpuset_size < 8 * sizeof (cpu_set_t)) 121 gomp_cpusetp 122 = (cpu_set_t *) gomp_realloc (gomp_cpusetp, gomp_cpuset_size); 123 else 124 { 125 /* Avoid gomp_fatal if too large memory allocation would be 126 requested, e.g. kernel returning EINVAL all the time. */ 127 void *p = realloc (gomp_cpusetp, gomp_cpuset_size); 128 if (p == NULL) 129 break; 130 gomp_cpusetp = (cpu_set_t *) p; 131 } 132 #else 133 break; 134 #endif 135 } 136 while (1); 137 gomp_cpuset_size = 0; 138 gomp_global_icv.nthreads_var = 1; 139 free (gomp_cpusetp); 140 gomp_cpusetp = NULL; 141 #endif 142 #ifdef _SC_NPROCESSORS_ONLN 143 gomp_global_icv.nthreads_var = sysconf (_SC_NPROCESSORS_ONLN); 144 #endif 145 } 146 147 static int 148 get_num_procs (void) 149 { 150 #ifdef HAVE_PTHREAD_AFFINITY_NP 151 if (gomp_places_list == NULL) 152 { 153 /* Count only the CPUs this process can use. */ 154 if (gomp_cpusetp 155 && pthread_getaffinity_np (pthread_self (), gomp_get_cpuset_size, 156 gomp_cpusetp) == 0) 157 { 158 int ret = gomp_cpuset_popcount (gomp_get_cpuset_size, gomp_cpusetp); 159 return ret != 0 ? ret : 1; 160 } 161 } 162 else 163 { 164 /* We can't use pthread_getaffinity_np in this case 165 (we have changed it ourselves, it binds to just one CPU). 166 Count instead the number of different CPUs we are 167 using. gomp_init_affinity updated gomp_available_cpus to 168 the number of CPUs in the GOMP_AFFINITY mask that we are 169 allowed to use though. */ 170 return gomp_available_cpus; 171 } 172 #endif 173 #ifdef _SC_NPROCESSORS_ONLN 174 return sysconf (_SC_NPROCESSORS_ONLN); 175 #else 176 return gomp_icv (false)->nthreads_var; 177 #endif 178 } 179 180 /* When OMP_DYNAMIC is set, at thread launch determine the number of 181 threads we should spawn for this team. */ 182 /* ??? I have no idea what best practice for this is. Surely some 183 function of the number of processors that are *still* online and 184 the load average. Here I use the number of processors online 185 minus the 15 minute load average. */ 186 187 unsigned 188 gomp_dynamic_max_threads (void) 189 { 190 unsigned n_onln, loadavg, nthreads_var = gomp_icv (false)->nthreads_var; 191 192 n_onln = get_num_procs (); 193 if (n_onln > nthreads_var) 194 n_onln = nthreads_var; 195 196 loadavg = 0; 197 #ifdef HAVE_GETLOADAVG 198 { 199 double dloadavg[3]; 200 if (getloadavg (dloadavg, 3) == 3) 201 { 202 /* Add 0.1 to get a kind of biased rounding. */ 203 loadavg = dloadavg[2] + 0.1; 204 } 205 } 206 #endif 207 208 if (loadavg >= n_onln) 209 return 1; 210 else 211 return n_onln - loadavg; 212 } 213 214 int 215 omp_get_num_procs (void) 216 { 217 return get_num_procs (); 218 } 219 220 ialias (omp_get_num_procs) 221
Indexes created Tue Feb 24 01:34:59 UTC 2026