proc.c revision 169696 
1/* Copyright (C) 2005, 2006 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
43
44/* At startup, determine the default number of threads.  It would seem
45   this should be related to the number of cpus online.  */
46
47void
48gomp_init_num_threads (void)
49{
50#ifdef _SC_NPROCESSORS_ONLN
51  gomp_nthreads_var = sysconf (_SC_NPROCESSORS_ONLN);
52#endif
53}
54
55/* When OMP_DYNAMIC is set, at thread launch determine the number of
56   threads we should spawn for this team.  */
57/* ??? I have no idea what best practice for this is.  Surely some
58   function of the number of processors that are *still* online and
59   the load average.  Here I use the number of processors online
60   minus the 15 minute load average.  */
61
62unsigned
63gomp_dynamic_max_threads (void)
64{
65  unsigned n_onln, loadavg;
66
67#ifdef _SC_NPROCESSORS_ONLN
68  n_onln = sysconf (_SC_NPROCESSORS_ONLN);
69  if (n_onln > gomp_nthreads_var)
70    n_onln = gomp_nthreads_var;
71#else
72  n_onln = gomp_nthreads_var;
73#endif
74
75  loadavg = 0;
76#ifdef HAVE_GETLOADAVG
77  {
78    double dloadavg[3];
79    if (getloadavg (dloadavg, 3) == 3)
80      {
81	/* Add 0.1 to get a kind of biased rounding.  */
82	loadavg = dloadavg[2] + 0.1;
83      }
84  }
85#endif
86
87  if (loadavg >= n_onln)
88    return 1;
89  else
90    return n_onln - loadavg;
91}
92
93int
94omp_get_num_procs (void)
95{
96#ifdef _SC_NPROCESSORS_ONLN
97  return sysconf (_SC_NPROCESSORS_ONLN);
98#else
99  return gomp_nthreads_var;
100#endif
101}
102
103ialias (omp_get_num_procs)
104