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/* Copyright (C) 2005, 2006, 2007, 2008, 2009 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 General Public License as published by
the Free Software Foundation; either version 3, 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 General Public License for
more details.
Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>. */
/* 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_global_icv.nthreads_var = cpuset_popcount (&cpuset);
if (gomp_global_icv.nthreads_var == 0)
gomp_global_icv.nthreads_var = 1;
return;
}
#endif
#ifdef _SC_NPROCESSORS_ONLN
gomp_global_icv.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_icv (false)->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, nthreads_var = gomp_icv (false)->nthreads_var;
n_onln = get_num_procs ();
if (n_onln > nthreads_var)
n_onln = 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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