1/* Copyright (C) 2005, 2006, 2007 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 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. */ 30 31#ifndef _GNU_SOURCE 32#define _GNU_SOURCE 1 33#endif 34#include "libgomp.h" 35#include <sched.h> 36#include <stdlib.h> 37#include <unistd.h> 38#ifdef HAVE_GETLOADAVG 39# ifdef HAVE_SYS_LOADAVG_H 40# include <sys/loadavg.h> 41# endif 42#endif 43 44#ifdef HAVE_PTHREAD_AFFINITY_NP 45static unsigned long 46cpuset_popcount (cpu_set_t *cpusetp) 47{ 48#ifdef CPU_COUNT 49 /* glibc 2.6 and above provide a macro for this. */ 50 return CPU_COUNT (cpusetp); 51#else 52 size_t i; 53 unsigned long ret = 0; 54 extern int check[sizeof (cpusetp->__bits[0]) == sizeof (unsigned long int)]; 55 56 (void) check; 57 for (i = 0; i < sizeof (*cpusetp) / sizeof (cpusetp->__bits[0]); i++) 58 { 59 unsigned long int mask = cpusetp->__bits[i]; 60 if (mask == 0) 61 continue; 62 ret += __builtin_popcountl (mask); 63 } 64 return ret; 65#endif 66} 67#endif 68 69/* At startup, determine the default number of threads. It would seem 70 this should be related to the number of cpus online. */ 71 72void 73gomp_init_num_threads (void) 74{ 75#ifdef HAVE_PTHREAD_AFFINITY_NP 76 cpu_set_t cpuset; 77 78 if (pthread_getaffinity_np (pthread_self (), sizeof (cpuset), &cpuset) == 0) 79 { 80 /* Count only the CPUs this process can use. */ 81 gomp_nthreads_var = cpuset_popcount (&cpuset); 82 if (gomp_nthreads_var == 0) 83 gomp_nthreads_var = 1; 84 return; 85 } 86#endif 87#ifdef _SC_NPROCESSORS_ONLN 88 gomp_nthreads_var = sysconf (_SC_NPROCESSORS_ONLN); 89#endif 90} 91 92static int 93get_num_procs (void) 94{ 95#ifdef HAVE_PTHREAD_AFFINITY_NP 96 cpu_set_t cpuset; 97 98 if (gomp_cpu_affinity == NULL) 99 { 100 /* Count only the CPUs this process can use. */ 101 if (pthread_getaffinity_np (pthread_self (), sizeof (cpuset), 102 &cpuset) == 0) 103 { 104 int ret = cpuset_popcount (&cpuset); 105 return ret != 0 ? ret : 1; 106 } 107 } 108 else 109 { 110 size_t idx; 111 static int affinity_cpus; 112 113 /* We can't use pthread_getaffinity_np in this case 114 (we have changed it ourselves, it binds to just one CPU). 115 Count instead the number of different CPUs we are 116 using. */ 117 CPU_ZERO (&cpuset); 118 if (affinity_cpus == 0) 119 { 120 int cpus = 0; 121 for (idx = 0; idx < gomp_cpu_affinity_len; idx++) 122 if (! CPU_ISSET (gomp_cpu_affinity[idx], &cpuset)) 123 { 124 cpus++; 125 CPU_SET (gomp_cpu_affinity[idx], &cpuset); 126 } 127 affinity_cpus = cpus; 128 } 129 return affinity_cpus; 130 } 131#endif 132#ifdef _SC_NPROCESSORS_ONLN 133 return sysconf (_SC_NPROCESSORS_ONLN); 134#else 135 return gomp_nthreads_var; 136#endif 137} 138 139/* When OMP_DYNAMIC is set, at thread launch determine the number of 140 threads we should spawn for this team. */ 141/* ??? I have no idea what best practice for this is. Surely some 142 function of the number of processors that are *still* online and 143 the load average. Here I use the number of processors online 144 minus the 15 minute load average. */ 145 146unsigned 147gomp_dynamic_max_threads (void) 148{ 149 unsigned n_onln, loadavg; 150 151 n_onln = get_num_procs (); 152 if (n_onln > gomp_nthreads_var) 153 n_onln = gomp_nthreads_var; 154 155 loadavg = 0; 156#ifdef HAVE_GETLOADAVG 157 { 158 double dloadavg[3]; 159 if (getloadavg (dloadavg, 3) == 3) 160 { 161 /* Add 0.1 to get a kind of biased rounding. */ 162 loadavg = dloadavg[2] + 0.1; 163 } 164 } 165#endif 166 167 if (loadavg >= n_onln) 168 return 1; 169 else 170 return n_onln - loadavg; 171} 172 173int 174omp_get_num_procs (void) 175{ 176 return get_num_procs (); 177} 178 179ialias (omp_get_num_procs) 180