libgomp/config/linux/proc.c

   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 <errno.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
  43 unsigned long gomp_cpuset_size;
  44 static unsigned long gomp_get_cpuset_size;
  45 cpu_set_t *gomp_cpusetp;
  46
  47 unsigned long
  48 gomp_cpuset_popcount (unsigned long cpusetsize, cpu_set_t *cpusetp)
  49 {
  50 #ifdef CPU_COUNT_S
  51   /* glibc 2.7 and above provide a macro for this.  */
  52   return CPU_COUNT_S (cpusetsize, cpusetp);
  53 #else
  54 #ifdef CPU_COUNT
  55   if (cpusetsize == sizeof (cpu_set_t))
  56     /* glibc 2.6 and above provide a macro for this.  */
  57     return CPU_COUNT (cpusetp);
  58 #endif
  59   size_t i;
  60   unsigned long ret = 0;
  61   extern int check[sizeof (cpusetp->__bits[0]) == sizeof (unsigned long int)
  62                    ? 1 : -1] __attribute__((unused));
  63
  64   for (i = 0; i < cpusetsize / sizeof (cpusetp->__bits[0]); i++)
  65     {
  66       unsigned long int mask = cpusetp->__bits[i];
  67       if (mask == 0)
  68         continue;
  69       ret += __builtin_popcountl (mask);
  70     }
  71   return ret;
  72 #endif
  73 }
  74 #endif
  75
  76 /* At startup, determine the default number of threads.  It would seem
  77    this should be related to the number of cpus online.  */
  78
  79 void
  80 gomp_init_num_threads (void)
  81 {
  82 #ifdef HAVE_PTHREAD_AFFINITY_NP
  83 #if defined (_SC_NPROCESSORS_CONF) && defined (CPU_ALLOC_SIZE)
  84   gomp_cpuset_size = sysconf (_SC_NPROCESSORS_CONF);
  85   gomp_cpuset_size = CPU_ALLOC_SIZE (gomp_cpuset_size);
  86 #else
  87   gomp_cpuset_size = sizeof (cpu_set_t);
  88 #endif
  89
  90   gomp_cpusetp = (cpu_set_t *) gomp_malloc (gomp_cpuset_size);
  91   do
  92     {
  93       int ret = pthread_getaffinity_np (pthread_self (), gomp_cpuset_size,
  94                                         gomp_cpusetp);
  95       if (ret == 0)
  96         {
  97           /* Count only the CPUs this process can use.  */
  98           gomp_global_icv.nthreads_var
  99             = gomp_cpuset_popcount (gomp_cpuset_size, gomp_cpusetp);
 100           if (gomp_global_icv.nthreads_var == 0)
 101             break;
 102           gomp_get_cpuset_size = gomp_cpuset_size;
 103 #ifdef CPU_ALLOC_SIZE
 104           unsigned long i;
 105           for (i = gomp_cpuset_size * 8; i; i--)
 106             if (CPU_ISSET_S (i - 1, gomp_cpuset_size, gomp_cpusetp))
 107               break;
 108           gomp_cpuset_size = CPU_ALLOC_SIZE (i);
 109 #endif
 110           return;
 111         }
 112       if (ret != EINVAL)
 113         break;
 114 #ifdef CPU_ALLOC_SIZE
 115       if (gomp_cpuset_size < sizeof (cpu_set_t))
 116         gomp_cpuset_size = sizeof (cpu_set_t);
 117       else
 118         gomp_cpuset_size = gomp_cpuset_size * 2;
 119       if (gomp_cpuset_size < 8 * sizeof (cpu_set_t))
 120         gomp_cpusetp
 121           = (cpu_set_t *) gomp_realloc (gomp_cpusetp, gomp_cpuset_size);
 122       else
 123         {
 124           /* Avoid gomp_fatal if too large memory allocation would be
 125              requested, e.g. kernel returning EINVAL all the time.  */
 126           void *p = realloc (gomp_cpusetp, gomp_cpuset_size);
 127           if (p == NULL)
 128             break;
 129           gomp_cpusetp = (cpu_set_t *) p;
 130         }
 131 #else
 132       break;
 133 #endif
 134     }
 135   while (1);
 136   gomp_cpuset_size = 0;
 137   gomp_global_icv.nthreads_var = 1;
 138   free (gomp_cpusetp);
 139   gomp_cpusetp = NULL;
 140 #endif
 141 #ifdef _SC_NPROCESSORS_ONLN
 142   gomp_global_icv.nthreads_var = sysconf (_SC_NPROCESSORS_ONLN);
 143 #endif
 144 }
 145
 146 static int
 147 get_num_procs (void)
 148 {
 149 #ifdef HAVE_PTHREAD_AFFINITY_NP
 150   if (gomp_places_list == NULL)
 151     {
 152       /* Count only the CPUs this process can use.  */
 153       if (gomp_cpusetp
 154           && pthread_getaffinity_np (pthread_self (), gomp_get_cpuset_size,
 155                                      gomp_cpusetp) == 0)
 156         {
 157           int ret = gomp_cpuset_popcount (gomp_get_cpuset_size, gomp_cpusetp);
 158           return ret != 0 ? ret : 1;
 159         }
 160     }
 161   else
 162     {
 163       /* We can't use pthread_getaffinity_np in this case
 164          (we have changed it ourselves, it binds to just one CPU).
 165          Count instead the number of different CPUs we are
 166          using.  gomp_init_affinity updated gomp_available_cpus to
 167          the number of CPUs in the GOMP_AFFINITY mask that we are
 168          allowed to use though.  */
 169       return gomp_available_cpus;
 170     }
 171 #endif
 172 #ifdef _SC_NPROCESSORS_ONLN
 173   return sysconf (_SC_NPROCESSORS_ONLN);
 174 #else
 175   return gomp_icv (false)->nthreads_var;
 176 #endif
 177 }
 178
 179 /* When OMP_DYNAMIC is set, at thread launch determine the number of
 180    threads we should spawn for this team.  */
 181 /* ??? I have no idea what best practice for this is.  Surely some
 182    function of the number of processors that are *still* online and
 183    the load average.  Here I use the number of processors online
 184    minus the 15 minute load average.  */
 185
 186 unsigned
 187 gomp_dynamic_max_threads (void)
 188 {
 189   unsigned n_onln, loadavg, nthreads_var = gomp_icv (false)->nthreads_var;
 190
 191   n_onln = get_num_procs ();
 192   if (n_onln > nthreads_var)
 193     n_onln = nthreads_var;
 194
 195   loadavg = 0;
 196 #ifdef HAVE_GETLOADAVG
 197   {
 198     double dloadavg[3];
 199     if (getloadavg (dloadavg, 3) == 3)
 200       {
 201         /* Add 0.1 to get a kind of biased rounding.  */
 202         loadavg = dloadavg[2] + 0.1;
 203       }
 204   }
 205 #endif
 206
 207   if (loadavg >= n_onln)
 208     return 1;
 209   else
 210     return n_onln - loadavg;
 211 }
 212
 213 int
 214 omp_get_num_procs (void)
 215 {
 216   return get_num_procs ();
 217 }
 218
 219 ialias (omp_get_num_procs)