proc.c revision 1.1.1.1.2.1 
1/* Copyright (C) 2005-2013 Free Software Foundation, Inc.
2   Contributed by Jakub Jelinek <jakub@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.  */
27
28#ifndef _GNU_SOURCE
29#define _GNU_SOURCE 1
30#endif
31#include "libgomp.h"
32#include "proc.h"
33#include <stdlib.h>
34#include <unistd.h>
35#ifdef HAVE_GETLOADAVG
36# ifdef HAVE_SYS_LOADAVG_H
37#  include <sys/loadavg.h>
38# endif
39#endif
40
41#ifdef HAVE_PTHREAD_AFFINITY_NP
42unsigned long
43gomp_cpuset_popcount (cpu_set_t *cpusetp)
44{
45#ifdef CPU_COUNT
46  /* glibc 2.6 and above provide a macro for this.  */
47  return CPU_COUNT (cpusetp);
48#else
49  size_t i;
50  unsigned long ret = 0;
51  extern int check[sizeof (cpusetp->__bits[0]) == sizeof (unsigned long int)];
52
53  (void) check;
54  for (i = 0; i < sizeof (*cpusetp) / sizeof (cpusetp->__bits[0]); i++)
55    {
56      unsigned long int mask = cpusetp->__bits[i];
57      if (mask == 0)
58	continue;
59      ret += __builtin_popcountl (mask);
60    }
61  return ret;
62#endif
63}
64#endif
65
66/* At startup, determine the default number of threads.  It would seem
67   this should be related to the number of cpus online.  */
68
69void
70gomp_init_num_threads (void)
71{
72#ifdef HAVE_PTHREAD_AFFINITY_NP
73  cpu_set_t cpuset;
74
75  if (pthread_getaffinity_np (pthread_self (), sizeof (cpuset), &cpuset) == 0)
76    {
77      /* Count only the CPUs this process can use.  */
78      gomp_global_icv.nthreads_var = gomp_cpuset_popcount (&cpuset);
79      if (gomp_global_icv.nthreads_var == 0)
80	gomp_global_icv.nthreads_var = 1;
81      return;
82    }
83#endif
84#ifdef _SC_NPROCESSORS_ONLN
85  gomp_global_icv.nthreads_var = sysconf (_SC_NPROCESSORS_ONLN);
86#endif
87}
88
89static int
90get_num_procs (void)
91{
92#ifdef HAVE_PTHREAD_AFFINITY_NP
93  cpu_set_t cpuset;
94
95  if (gomp_cpu_affinity == NULL)
96    {
97      /* Count only the CPUs this process can use.  */
98      if (pthread_getaffinity_np (pthread_self (), sizeof (cpuset),
99				  &cpuset) == 0)
100	{
101	  int ret = gomp_cpuset_popcount (&cpuset);
102	  return ret != 0 ? ret : 1;
103	}
104    }
105  else
106    {
107      /* We can't use pthread_getaffinity_np in this case
108	 (we have changed it ourselves, it binds to just one CPU).
109	 Count instead the number of different CPUs we are
110	 using.  gomp_init_affinity updated gomp_available_cpus to
111	 the number of CPUs in the GOMP_AFFINITY mask that we are
112	 allowed to use though.  */
113      return gomp_available_cpus;
114    }
115#endif
116#ifdef _SC_NPROCESSORS_ONLN
117  return sysconf (_SC_NPROCESSORS_ONLN);
118#else
119  return gomp_icv (false)->nthreads_var;
120#endif
121}
122
123/* When OMP_DYNAMIC is set, at thread launch determine the number of
124   threads we should spawn for this team.  */
125/* ??? I have no idea what best practice for this is.  Surely some
126   function of the number of processors that are *still* online and
127   the load average.  Here I use the number of processors online
128   minus the 15 minute load average.  */
129
130unsigned
131gomp_dynamic_max_threads (void)
132{
133  unsigned n_onln, loadavg, nthreads_var = gomp_icv (false)->nthreads_var;
134
135  n_onln = get_num_procs ();
136  if (n_onln > nthreads_var)
137    n_onln = nthreads_var;
138
139  loadavg = 0;
140#ifdef HAVE_GETLOADAVG
141  {
142    double dloadavg[3];
143    if (getloadavg (dloadavg, 3) == 3)
144      {
145	/* Add 0.1 to get a kind of biased rounding.  */
146	loadavg = dloadavg[2] + 0.1;
147      }
148  }
149#endif
150
151  if (loadavg >= n_onln)
152    return 1;
153  else
154    return n_onln - loadavg;
155}
156
157int
158omp_get_num_procs (void)
159{
160  return get_num_procs ();
161}
162
163ialias (omp_get_num_procs)
164