1/* Copyright (C) 2005, 2006, 2008 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 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.  It is expected that
30   a system may well want to write special versions of each of these.
31
32   The following implementation uses a mix of POSIX and BSD routines.  */
33
34#include "libgomp.h"
35#include <unistd.h>
36#include <stdlib.h>
37#ifdef HAVE_GETLOADAVG
38# ifdef HAVE_SYS_LOADAVG_H
39#  include <sys/loadavg.h>
40# endif
41#endif
42#ifdef HAVE_SYS_SYSCTL_H
43# include <sys/sysctl.h>
44#endif
45
46static int
47get_num_procs (void)
48{
49#ifdef _SC_NPROCESSORS_ONLN
50  return sysconf (_SC_NPROCESSORS_ONLN);
51#elif defined HW_NCPU
52  int ncpus = 1;
53  size_t len = sizeof(ncpus);
54  sysctl((int[2]) {CTL_HW, HW_NCPU}, 2, &ncpus, &len, NULL, 0);
55  return ncpus;
56#else
57  return 0;
58#endif
59}
60
61/* At startup, determine the default number of threads.  It would seem
62   this should be related to the number of cpus online.  */
63
64void
65gomp_init_num_threads (void)
66{
67  int ncpus = get_num_procs ();
68
69  if (ncpus > 0)
70    gomp_global_icv.nthreads_var = ncpus;
71}
72
73/* When OMP_DYNAMIC is set, at thread launch determine the number of
74   threads we should spawn for this team.  */
75/* ??? I have no idea what best practice for this is.  Surely some
76   function of the number of processors that are *still* online and
77   the load average.  Here I use the number of processors online
78   minus the 15 minute load average.  */
79
80unsigned
81gomp_dynamic_max_threads (void)
82{
83  unsigned n_onln, loadavg;
84  unsigned nthreads_var = gomp_icv (false)->nthreads_var;
85
86  n_onln = get_num_procs ();
87  if (!n_onln || n_onln > nthreads_var)
88    n_onln = nthreads_var;
89
90  loadavg = 0;
91#ifdef HAVE_GETLOADAVG
92  {
93    double dloadavg[3];
94    if (getloadavg (dloadavg, 3) == 3)
95      {
96	/* Add 0.1 to get a kind of biased rounding.  */
97	loadavg = dloadavg[2] + 0.1;
98      }
99  }
100#endif
101
102  if (loadavg >= n_onln)
103    return 1;
104  else
105    return n_onln - loadavg;
106}
107
108int
109omp_get_num_procs (void)
110{
111  int ncpus = get_num_procs ();
112  if (ncpus <= 0)
113    ncpus = gomp_icv (false)->nthreads_var;
114  return ncpus;
115}
116
117ialias (omp_get_num_procs)
118