1/* Copyright (C) 2005-2020 Free Software Foundation, Inc. 2 Contributed by Richard Henderson <rth@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. It is expected that 28 a system may well want to write special versions of each of these. 29 30 The following implementation uses a mix of POSIX and BSD routines. */ 31 32#include "libgomp.h" 33#include <unistd.h> 34#include <stdlib.h> 35#ifdef HAVE_GETLOADAVG 36# ifdef HAVE_SYS_LOADAVG_H 37# include <sys/loadavg.h> 38# endif 39#endif 40#ifdef HAVE_SYS_SYSCTL_H 41# include <sys/sysctl.h> 42#endif 43 44static int 45get_num_procs (void) 46{ 47#ifdef _SC_NPROCESSORS_ONLN 48 return sysconf (_SC_NPROCESSORS_ONLN); 49#elif defined HW_NCPU 50 int ncpus = 1; 51 size_t len = sizeof(ncpus); 52 sysctl((int[2]) {CTL_HW, HW_NCPU}, 2, &ncpus, &len, NULL, 0); 53 return ncpus; 54#else 55 return 0; 56#endif 57} 58 59/* At startup, determine the default number of threads. It would seem 60 this should be related to the number of cpus online. */ 61 62void 63gomp_init_num_threads (void) 64{ 65 int ncpus = get_num_procs (); 66 67 if (ncpus > 0) 68 gomp_global_icv.nthreads_var = ncpus; 69} 70 71/* When OMP_DYNAMIC is set, at thread launch determine the number of 72 threads we should spawn for this team. */ 73/* ??? I have no idea what best practice for this is. Surely some 74 function of the number of processors that are *still* online and 75 the load average. Here I use the number of processors online 76 minus the 15 minute load average. */ 77 78unsigned 79gomp_dynamic_max_threads (void) 80{ 81 unsigned n_onln, loadavg; 82 unsigned nthreads_var = gomp_icv (false)->nthreads_var; 83 84 n_onln = get_num_procs (); 85 if (!n_onln || n_onln > nthreads_var) 86 n_onln = nthreads_var; 87 88 loadavg = 0; 89#ifdef HAVE_GETLOADAVG 90 { 91 double dloadavg[3]; 92 if (getloadavg (dloadavg, 3) == 3) 93 { 94 /* Add 0.1 to get a kind of biased rounding. */ 95 loadavg = dloadavg[2] + 0.1; 96 } 97 } 98#endif 99 100 if (loadavg >= n_onln) 101 return 1; 102 else 103 return n_onln - loadavg; 104} 105 106int 107omp_get_num_procs (void) 108{ 109 int ncpus = get_num_procs (); 110 if (ncpus <= 0) 111 ncpus = gomp_icv (false)->nthreads_var; 112 return ncpus; 113} 114 115ialias (omp_get_num_procs) 116