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