1 /* Copyright (C) 2005, 2006, 2007 Free Software Foundation, Inc.
2 Contributed by Jakub Jelinek <[email protected]>.
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. */
30
31 #ifndef _GNU_SOURCE
32 #define _GNU_SOURCE 1
33 #endif
34 #include "libgomp.h"
35 #include <sched.h>
36 #include <stdlib.h>
37 #include <unistd.h>
38 #ifdef HAVE_GETLOADAVG
39 # ifdef HAVE_SYS_LOADAVG_H
40 # include <sys/loadavg.h>
41 # endif
42 #endif
43
44 #ifdef HAVE_PTHREAD_AFFINITY_NP
45 static unsigned long
cpuset_popcount(cpu_set_t * cpusetp)46 cpuset_popcount (cpu_set_t *cpusetp)
47 {
48 #ifdef CPU_COUNT
49 /* glibc 2.6 and above provide a macro for this. */
50 return CPU_COUNT (cpusetp);
51 #else
52 size_t i;
53 unsigned long ret = 0;
54 extern int check[sizeof (cpusetp->__bits[0]) == sizeof (unsigned long int)];
55
56 (void) check;
57 for (i = 0; i < sizeof (*cpusetp) / sizeof (cpusetp->__bits[0]); i++)
58 {
59 unsigned long int mask = cpusetp->__bits[i];
60 if (mask == 0)
61 continue;
62 ret += __builtin_popcountl (mask);
63 }
64 return ret;
65 #endif
66 }
67 #endif
68
69 /* At startup, determine the default number of threads. It would seem
70 this should be related to the number of cpus online. */
71
72 void
gomp_init_num_threads(void)73 gomp_init_num_threads (void)
74 {
75 #ifdef HAVE_PTHREAD_AFFINITY_NP
76 cpu_set_t cpuset;
77
78 if (pthread_getaffinity_np (pthread_self (), sizeof (cpuset), &cpuset) == 0)
79 {
80 /* Count only the CPUs this process can use. */
81 gomp_nthreads_var = cpuset_popcount (&cpuset);
82 if (gomp_nthreads_var == 0)
83 gomp_nthreads_var = 1;
84 return;
85 }
86 #endif
87 #ifdef _SC_NPROCESSORS_ONLN
88 gomp_nthreads_var = sysconf (_SC_NPROCESSORS_ONLN);
89 #endif
90 }
91
92 static int
get_num_procs(void)93 get_num_procs (void)
94 {
95 #ifdef HAVE_PTHREAD_AFFINITY_NP
96 cpu_set_t cpuset;
97
98 if (gomp_cpu_affinity == NULL)
99 {
100 /* Count only the CPUs this process can use. */
101 if (pthread_getaffinity_np (pthread_self (), sizeof (cpuset),
102 &cpuset) == 0)
103 {
104 int ret = cpuset_popcount (&cpuset);
105 return ret != 0 ? ret : 1;
106 }
107 }
108 else
109 {
110 size_t idx;
111 static int affinity_cpus;
112
113 /* We can't use pthread_getaffinity_np in this case
114 (we have changed it ourselves, it binds to just one CPU).
115 Count instead the number of different CPUs we are
116 using. */
117 CPU_ZERO (&cpuset);
118 if (affinity_cpus == 0)
119 {
120 int cpus = 0;
121 for (idx = 0; idx < gomp_cpu_affinity_len; idx++)
122 if (! CPU_ISSET (gomp_cpu_affinity[idx], &cpuset))
123 {
124 cpus++;
125 CPU_SET (gomp_cpu_affinity[idx], &cpuset);
126 }
127 affinity_cpus = cpus;
128 }
129 return affinity_cpus;
130 }
131 #endif
132 #ifdef _SC_NPROCESSORS_ONLN
133 return sysconf (_SC_NPROCESSORS_ONLN);
134 #else
135 return gomp_nthreads_var;
136 #endif
137 }
138
139 /* When OMP_DYNAMIC is set, at thread launch determine the number of
140 threads we should spawn for this team. */
141 /* ??? I have no idea what best practice for this is. Surely some
142 function of the number of processors that are *still* online and
143 the load average. Here I use the number of processors online
144 minus the 15 minute load average. */
145
146 unsigned
gomp_dynamic_max_threads(void)147 gomp_dynamic_max_threads (void)
148 {
149 unsigned n_onln, loadavg;
150
151 n_onln = get_num_procs ();
152 if (n_onln > gomp_nthreads_var)
153 n_onln = gomp_nthreads_var;
154
155 loadavg = 0;
156 #ifdef HAVE_GETLOADAVG
157 {
158 double dloadavg[3];
159 if (getloadavg (dloadavg, 3) == 3)
160 {
161 /* Add 0.1 to get a kind of biased rounding. */
162 loadavg = dloadavg[2] + 0.1;
163 }
164 }
165 #endif
166
167 if (loadavg >= n_onln)
168 return 1;
169 else
170 return n_onln - loadavg;
171 }
172
173 int
omp_get_num_procs(void)174 omp_get_num_procs (void)
175 {
176 return get_num_procs ();
177 }
178
179 ialias (omp_get_num_procs)
180