1 /* Copyright (C) 2005, 2006, 2008, 2009 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 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. It is expected that 27 a system may well want to write special versions of each of these. 28 29 The following implementation uses a mix of POSIX and BSD routines. */ 30 31 #include "libgomp.h" 32 #include <unistd.h> 33 #include <stdlib.h> 34 #ifdef HAVE_GETLOADAVG 35 # ifdef HAVE_SYS_LOADAVG_H 36 # include <sys/loadavg.h> 37 # endif 38 #endif 39 #ifdef HAVE_SYS_SYSCTL_H 40 # include <sys/sysctl.h> 41 #endif 42 43 static int 44 get_num_procs (void) 45 { 46 #ifdef _SC_NPROCESSORS_ONLN 47 return sysconf (_SC_NPROCESSORS_ONLN); 48 #elif defined HW_NCPU 49 int ncpus = 1; 50 size_t len = sizeof(ncpus); 51 sysctl((int[2]) {CTL_HW, HW_NCPU}, 2, &ncpus, &len, NULL, 0); 52 return ncpus; 53 #else 54 return 0; 55 #endif 56 } 57 58 /* At startup, determine the default number of threads. It would seem 59 this should be related to the number of cpus online. */ 60 61 void 62 gomp_init_num_threads (void) 63 { 64 int ncpus = get_num_procs (); 65 66 if (ncpus > 0) 67 gomp_global_icv.nthreads_var = ncpus; 68 } 69 70 /* When OMP_DYNAMIC is set, at thread launch determine the number of 71 threads we should spawn for this team. */ 72 /* ??? I have no idea what best practice for this is. Surely some 73 function of the number of processors that are *still* online and 74 the load average. Here I use the number of processors online 75 minus the 15 minute load average. */ 76 77 unsigned 78 gomp_dynamic_max_threads (void) 79 { 80 unsigned n_onln, loadavg; 81 unsigned nthreads_var = gomp_icv (false)->nthreads_var; 82 83 n_onln = get_num_procs (); 84 if (!n_onln || n_onln > nthreads_var) 85 n_onln = nthreads_var; 86 87 loadavg = 0; 88 #ifdef HAVE_GETLOADAVG 89 { 90 double dloadavg[3]; 91 if (getloadavg (dloadavg, 3) == 3) 92 { 93 /* Add 0.1 to get a kind of biased rounding. */ 94 loadavg = dloadavg[2] + 0.1; 95 } 96 } 97 #endif 98 99 if (loadavg >= n_onln) 100 return 1; 101 else 102 return n_onln - loadavg; 103 } 104 105 int 106 omp_get_num_procs (void) 107 { 108 int ncpus = get_num_procs (); 109 if (ncpus <= 0) 110 ncpus = gomp_icv (false)->nthreads_var; 111 return ncpus; 112 } 113 114 ialias (omp_get_num_procs) 115