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