libgomp/config/linux/proc.c

   1 /* Copyright (C) 2005-2019 Free Software Foundation, Inc.
   2    Contributed by Jakub Jelinek <jakub@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.  */
  28
  29 #ifndef _GNU_SOURCE
  30 #define _GNU_SOURCE 1
  31 #endif
  32 #include "libgomp.h"
  33 #include "proc.h"
  34 #include <errno.h>
  35 #include <stdlib.h>
  36 #include <unistd.h>
  37 #ifdef HAVE_GETLOADAVG
  38 # ifdef HAVE_SYS_LOADAVG_H
  39 #  include <sys/loadavg.h>
  40 # endif
  41 #endif
  42
  43 #ifdef HAVE_PTHREAD_AFFINITY_NP
  44 unsigned long gomp_cpuset_size;
  45 static unsigned long gomp_get_cpuset_size;
  46 cpu_set_t *gomp_cpusetp;
  47
  48 unsigned long
  49 gomp_cpuset_popcount (unsigned long cpusetsize, cpu_set_t *cpusetp)
  50 {
  51 #ifdef CPU_COUNT_S
  52   /* glibc 2.7 and above provide a macro for this.  */
  53   return CPU_COUNT_S (cpusetsize, cpusetp);
  54 #else
  55 #ifdef CPU_COUNT
  56   if (cpusetsize == sizeof (cpu_set_t))
  57     /* glibc 2.6 and above provide a macro for this.  */
  58     return CPU_COUNT (cpusetp);
  59 #endif
  60   size_t i;
  61   unsigned long ret = 0;
  62   extern int check[sizeof (cpusetp->__bits[0]) == sizeof (unsigned long int)
  63                    ? 1 : -1] __attribute__((unused));
  64
  65   for (i = 0; i < cpusetsize / sizeof (cpusetp->__bits[0]); i++)
  66     {
  67       unsigned long int mask = cpusetp->__bits[i];
  68       if (mask == 0)
  69         continue;
  70       ret += __builtin_popcountl (mask);
  71     }
  72   return ret;
  73 #endif
  74 }
  75 #endif
  76
  77 /* At startup, determine the default number of threads.  It would seem
  78    this should be related to the number of cpus online.  */
  79
  80 void
  81 gomp_init_num_threads (void)
  82 {
  83 #ifdef HAVE_PTHREAD_AFFINITY_NP
  84 #if defined (_SC_NPROCESSORS_CONF) && defined (CPU_ALLOC_SIZE)
  85   gomp_cpuset_size = sysconf (_SC_NPROCESSORS_CONF);
  86   gomp_cpuset_size = CPU_ALLOC_SIZE (gomp_cpuset_size);
  87 #else
  88   gomp_cpuset_size = sizeof (cpu_set_t);
  89 #endif
  90
  91   gomp_cpusetp = (cpu_set_t *) gomp_malloc (gomp_cpuset_size);
  92   do
  93     {
  94       int ret = pthread_getaffinity_np (pthread_self (), gomp_cpuset_size,
  95                                         gomp_cpusetp);
  96       if (ret == 0)
  97         {
  98           /* Count only the CPUs this process can use.  */
  99           gomp_global_icv.nthreads_var
 100             = gomp_cpuset_popcount (gomp_cpuset_size, gomp_cpusetp);
 101           if (gomp_global_icv.nthreads_var == 0)
 102             break;
 103           gomp_get_cpuset_size = gomp_cpuset_size;
 104 #ifdef CPU_ALLOC_SIZE
 105           unsigned long i;
 106           for (i = gomp_cpuset_size * 8; i; i--)
 107             if (CPU_ISSET_S (i - 1, gomp_cpuset_size, gomp_cpusetp))
 108               break;
 109           gomp_cpuset_size = CPU_ALLOC_SIZE (i);
 110 #endif
 111           return;
 112         }
 113       if (ret != EINVAL)
 114         break;
 115 #ifdef CPU_ALLOC_SIZE
 116       if (gomp_cpuset_size < sizeof (cpu_set_t))
 117         gomp_cpuset_size = sizeof (cpu_set_t);
 118       else
 119         gomp_cpuset_size = gomp_cpuset_size * 2;
 120       if (gomp_cpuset_size < 8 * sizeof (cpu_set_t))
 121         gomp_cpusetp
 122           = (cpu_set_t *) gomp_realloc (gomp_cpusetp, gomp_cpuset_size);
 123       else
 124         {
 125           /* Avoid gomp_fatal if too large memory allocation would be
 126              requested, e.g. kernel returning EINVAL all the time.  */
 127           void *p = realloc (gomp_cpusetp, gomp_cpuset_size);
 128           if (p == NULL)
 129             break;
 130           gomp_cpusetp = (cpu_set_t *) p;
 131         }
 132 #else
 133       break;
 134 #endif
 135     }
 136   while (1);
 137   gomp_cpuset_size = 0;
 138   gomp_global_icv.nthreads_var = 1;
 139   free (gomp_cpusetp);
 140   gomp_cpusetp = NULL;
 141 #endif
 142 #ifdef _SC_NPROCESSORS_ONLN
 143   gomp_global_icv.nthreads_var = sysconf (_SC_NPROCESSORS_ONLN);
 144 #endif
 145 }
 146
 147 static int
 148 get_num_procs (void)
 149 {
 150 #ifdef HAVE_PTHREAD_AFFINITY_NP
 151   if (gomp_places_list == NULL)
 152     {
 153       /* Count only the CPUs this process can use.  */
 154       if (gomp_cpusetp
 155           && pthread_getaffinity_np (pthread_self (), gomp_get_cpuset_size,
 156                                      gomp_cpusetp) == 0)
 157         {
 158           int ret = gomp_cpuset_popcount (gomp_get_cpuset_size, gomp_cpusetp);
 159           return ret != 0 ? ret : 1;
 160         }
 161     }
 162   else
 163     {
 164       /* We can't use pthread_getaffinity_np in this case
 165          (we have changed it ourselves, it binds to just one CPU).
 166          Count instead the number of different CPUs we are
 167          using.  gomp_init_affinity updated gomp_available_cpus to
 168          the number of CPUs in the GOMP_AFFINITY mask that we are
 169          allowed to use though.  */
 170       return gomp_available_cpus;
 171     }
 172 #endif
 173 #ifdef _SC_NPROCESSORS_ONLN
 174   return sysconf (_SC_NPROCESSORS_ONLN);
 175 #else
 176   return gomp_icv (false)->nthreads_var;
 177 #endif
 178 }
 179
 180 /* When OMP_DYNAMIC is set, at thread launch determine the number of
 181    threads we should spawn for this team.  */
 182 /* ??? I have no idea what best practice for this is.  Surely some
 183    function of the number of processors that are *still* online and
 184    the load average.  Here I use the number of processors online
 185    minus the 15 minute load average.  */
 186
 187 unsigned
 188 gomp_dynamic_max_threads (void)
 189 {
 190   unsigned n_onln, loadavg, nthreads_var = gomp_icv (false)->nthreads_var;
 191
 192   n_onln = get_num_procs ();
 193   if (n_onln > nthreads_var)
 194     n_onln = nthreads_var;
 195
 196   loadavg = 0;
 197 #ifdef HAVE_GETLOADAVG
 198   {
 199     double dloadavg[3];
 200     if (getloadavg (dloadavg, 3) == 3)
 201       {
 202         /* Add 0.1 to get a kind of biased rounding.  */
 203         loadavg = dloadavg[2] + 0.1;
 204       }
 205   }
 206 #endif
 207
 208   if (loadavg >= n_onln)
 209     return 1;
 210   else
 211     return n_onln - loadavg;
 212 }
 213
 214 int
 215 omp_get_num_procs (void)
 216 {
 217   return get_num_procs ();
 218 }
 219
 220 ialias (omp_get_num_procs)