source: trunk/sys/libgomp/proc.c @ 1

Last change on this file since 1 was 1, checked in by alain, 5 years ago

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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 <gomp/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
40
41/* At startup, determine the default number of threads.  It would seem
42   this should be related to the number of cpus online.  */
43
44void
45gomp_init_num_threads (void)
46{
47#ifdef _SC_NPROCESSORS_ONLN
48  gomp_global_icv.nthreads_var = sysconf (_SC_NPROCESSORS_ONLN);
49#endif
50}
51
52/* When OMP_DYNAMIC is set, at thread launch determine the number of
53   threads we should spawn for this team.  */
54/* ??? I have no idea what best practice for this is.  Surely some
55   function of the number of processors that are *still* online and
56   the load average.  Here I use the number of processors online
57   minus the 15 minute load average.  */
58
59unsigned
60gomp_dynamic_max_threads (void)
61{
62  unsigned n_onln, loadavg;
63  unsigned nthreads_var = gomp_icv (false)->nthreads_var;
64
65#ifdef _SC_NPROCESSORS_ONLN
66  n_onln = sysconf (_SC_NPROCESSORS_ONLN);
67  if (n_onln > nthreads_var)
68    n_onln = nthreads_var;
69#else
70  n_onln = nthreads_var;
71#endif
72
73  loadavg = 0;
74#ifdef HAVE_GETLOADAVG
75  {
76    double dloadavg[3];
77    if (getloadavg (dloadavg, 3) == 3)
78      {
79        /* Add 0.1 to get a kind of biased rounding.  */
80        loadavg = dloadavg[2] + 0.1;
81      }
82  }
83#endif
84
85  if (loadavg >= n_onln)
86    return 1;
87  else
88    return n_onln - loadavg;
89}
90
91int
92omp_get_num_procs(void)
93{
94#ifdef _SC_NPROCESSORS_ONLN
95  return sysconf (_SC_NPROCESSORS_ONLN);
96#else
97  return gomp_icv (false)->nthreads_var;
98#endif
99}
100
101ialias (omp_get_num_procs)
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