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/* Copyright (C) 2005, 2006, 2007 Free Software Foundation, Inc.
Contributed by Jakub Jelinek <jakub@redhat.com>.
This file is part of the GNU OpenMP Library (libgomp).
Libgomp is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
more details.
You should have received a copy of the GNU Lesser General Public License
along with libgomp; see the file COPYING.LIB. If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
MA 02110-1301, USA. */
/* As a special exception, if you link this library with other files, some
of which are compiled with GCC, to produce an executable, this library
does not by itself cause the resulting executable to be covered by the
GNU General Public License. This exception does not however invalidate
any other reasons why the executable file might be covered by the GNU
General Public License. */
/* This file contains system specific routines related to counting
online processors and dynamic load balancing. */
#ifndef _GNU_SOURCE
#define _GNU_SOURCE 1
#endif
#include "libgomp.h"
#include <sched.h>
#include <stdlib.h>
#include <unistd.h>
#ifdef HAVE_GETLOADAVG
# ifdef HAVE_SYS_LOADAVG_H
# include <sys/loadavg.h>
# endif
#endif
#ifdef HAVE_PTHREAD_AFFINITY_NP
static unsigned long
cpuset_popcount (cpu_set_t *cpusetp)
{
#ifdef CPU_COUNT
/* glibc 2.6 and above provide a macro for this. */
return CPU_COUNT (cpusetp);
#else
size_t i;
unsigned long ret = 0;
extern int check[sizeof (cpusetp->__bits[0]) == sizeof (unsigned long int)];
(void) check;
for (i = 0; i < sizeof (*cpusetp) / sizeof (cpusetp->__bits[0]); i++)
{
unsigned long int mask = cpusetp->__bits[i];
if (mask == 0)
continue;
ret += __builtin_popcountl (mask);
}
return ret;
#endif
}
#endif
/* At startup, determine the default number of threads. It would seem
this should be related to the number of cpus online. */
void
gomp_init_num_threads (void)
{
#ifdef HAVE_PTHREAD_AFFINITY_NP
cpu_set_t cpuset;
if (pthread_getaffinity_np (pthread_self (), sizeof (cpuset), &cpuset) == 0)
{
/* Count only the CPUs this process can use. */
gomp_nthreads_var = cpuset_popcount (&cpuset);
if (gomp_nthreads_var == 0)
gomp_nthreads_var = 1;
return;
}
#endif
#ifdef _SC_NPROCESSORS_ONLN
gomp_nthreads_var = sysconf (_SC_NPROCESSORS_ONLN);
#endif
}
static int
get_num_procs (void)
{
#ifdef HAVE_PTHREAD_AFFINITY_NP
cpu_set_t cpuset;
if (gomp_cpu_affinity == NULL)
{
/* Count only the CPUs this process can use. */
if (pthread_getaffinity_np (pthread_self (), sizeof (cpuset),
&cpuset) == 0)
{
int ret = cpuset_popcount (&cpuset);
return ret != 0 ? ret : 1;
}
}
else
{
size_t idx;
static int affinity_cpus;
/* We can't use pthread_getaffinity_np in this case
(we have changed it ourselves, it binds to just one CPU).
Count instead the number of different CPUs we are
using. */
CPU_ZERO (&cpuset);
if (affinity_cpus == 0)
{
int cpus = 0;
for (idx = 0; idx < gomp_cpu_affinity_len; idx++)
if (! CPU_ISSET (gomp_cpu_affinity[idx], &cpuset))
{
cpus++;
CPU_SET (gomp_cpu_affinity[idx], &cpuset);
}
affinity_cpus = cpus;
}
return affinity_cpus;
}
#endif
#ifdef _SC_NPROCESSORS_ONLN
return sysconf (_SC_NPROCESSORS_ONLN);
#else
return gomp_nthreads_var;
#endif
}
/* When OMP_DYNAMIC is set, at thread launch determine the number of
threads we should spawn for this team. */
/* ??? I have no idea what best practice for this is. Surely some
function of the number of processors that are *still* online and
the load average. Here I use the number of processors online
minus the 15 minute load average. */
unsigned
gomp_dynamic_max_threads (void)
{
unsigned n_onln, loadavg;
n_onln = get_num_procs ();
if (n_onln > gomp_nthreads_var)
n_onln = gomp_nthreads_var;
loadavg = 0;
#ifdef HAVE_GETLOADAVG
{
double dloadavg[3];
if (getloadavg (dloadavg, 3) == 3)
{
/* Add 0.1 to get a kind of biased rounding. */
loadavg = dloadavg[2] + 0.1;
}
}
#endif
if (loadavg >= n_onln)
return 1;
else
return n_onln - loadavg;
}
int
omp_get_num_procs (void)
{
return get_num_procs ();
}
ialias (omp_get_num_procs)
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