proc.c revision 1.1 
1/* Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010
2   Free Software Foundation, Inc.
3   Contributed by Jakub Jelinek <jakub@redhat.com>.
4
5   This file is part of the GNU OpenMP Library (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.  */
28
29#ifndef _GNU_SOURCE
30#define _GNU_SOURCE 1
31#endif
32#include "libgomp.h"
33#include <sched.h>
34#include <stdlib.h>
35#include <unistd.h>
36#ifdef HAVE_GETLOADAVG
37# ifdef HAVE_SYS_LOADAVG_H
38#  include <sys/loadavg.h>
39# endif
40#endif
41
42#ifdef HAVE_PTHREAD_AFFINITY_NP
43static unsigned long
44cpuset_popcount (cpu_set_t *cpusetp)
45{
46#ifdef CPU_COUNT
47  /* glibc 2.6 and above provide a macro for this.  */
48  return CPU_COUNT (cpusetp);
49#else
50  size_t i;
51  unsigned long ret = 0;
52  extern int check[sizeof (cpusetp->__bits[0]) == sizeof (unsigned long int)];
53
54  (void) check;
55  for (i = 0; i < sizeof (*cpusetp) / sizeof (cpusetp->__bits[0]); i++)
56    {
57      unsigned long int mask = cpusetp->__bits[i];
58      if (mask == 0)
59	continue;
60      ret += __builtin_popcountl (mask);
61    }
62  return ret;
63#endif
64}
65#endif
66
67/* At startup, determine the default number of threads.  It would seem
68   this should be related to the number of cpus online.  */
69
70void
71gomp_init_num_threads (void)
72{
73#ifdef HAVE_PTHREAD_AFFINITY_NP
74  cpu_set_t cpuset;
75
76  if (pthread_getaffinity_np (pthread_self (), sizeof (cpuset), &cpuset) == 0)
77    {
78      /* Count only the CPUs this process can use.  */
79      gomp_global_icv.nthreads_var = cpuset_popcount (&cpuset);
80      if (gomp_global_icv.nthreads_var == 0)
81	gomp_global_icv.nthreads_var = 1;
82      return;
83    }
84#endif
85#ifdef _SC_NPROCESSORS_ONLN
86  gomp_global_icv.nthreads_var = sysconf (_SC_NPROCESSORS_ONLN);
87#endif
88}
89
90static int
91get_num_procs (void)
92{
93#ifdef HAVE_PTHREAD_AFFINITY_NP
94  cpu_set_t cpuset;
95
96  if (gomp_cpu_affinity == NULL)
97    {
98      /* Count only the CPUs this process can use.  */
99      if (pthread_getaffinity_np (pthread_self (), sizeof (cpuset),
100				  &cpuset) == 0)
101	{
102	  int ret = cpuset_popcount (&cpuset);
103	  return ret != 0 ? ret : 1;
104	}
105    }
106  else
107    {
108      /* We can't use pthread_getaffinity_np in this case
109	 (we have changed it ourselves, it binds to just one CPU).
110	 Count instead the number of different CPUs we are
111	 using.  gomp_init_affinity updated gomp_available_cpus to
112	 the number of CPUs in the GOMP_AFFINITY mask that we are
113	 allowed to use though.  */
114      return gomp_available_cpus;
115    }
116#endif
117#ifdef _SC_NPROCESSORS_ONLN
118  return sysconf (_SC_NPROCESSORS_ONLN);
119#else
120  return gomp_icv (false)->nthreads_var;
121#endif
122}
123
124/* When OMP_DYNAMIC is set, at thread launch determine the number of
125   threads we should spawn for this team.  */
126/* ??? I have no idea what best practice for this is.  Surely some
127   function of the number of processors that are *still* online and
128   the load average.  Here I use the number of processors online
129   minus the 15 minute load average.  */
130
131unsigned
132gomp_dynamic_max_threads (void)
133{
134  unsigned n_onln, loadavg, nthreads_var = gomp_icv (false)->nthreads_var;
135
136  n_onln = get_num_procs ();
137  if (n_onln > nthreads_var)
138    n_onln = nthreads_var;
139
140  loadavg = 0;
141#ifdef HAVE_GETLOADAVG
142  {
143    double dloadavg[3];
144    if (getloadavg (dloadavg, 3) == 3)
145      {
146	/* Add 0.1 to get a kind of biased rounding.  */
147	loadavg = dloadavg[2] + 0.1;
148      }
149  }
150#endif
151
152  if (loadavg >= n_onln)
153    return 1;
154  else
155    return n_onln - loadavg;
156}
157
158int
159omp_get_num_procs (void)
160{
161  return get_num_procs ();
162}
163
164ialias (omp_get_num_procs)
165