116 lines
3.1 KiB
C
116 lines
3.1 KiB
C
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/* Copyright (C) 2005-2022 Free Software Foundation, Inc.
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Contributed by Richard Henderson <rth@redhat.com>.
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This file is part of the GNU Offloading and Multi Processing Library
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(libgomp).
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Libgomp is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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more details.
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Under Section 7 of GPL version 3, you are granted additional
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permissions described in the GCC Runtime Library Exception, version
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3.1, as published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License and
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a copy of the GCC Runtime Library Exception along with this program;
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see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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<http://www.gnu.org/licenses/>. */
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/* This file contains system specific routines related to counting
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online processors and dynamic load balancing. It is expected that
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a system may well want to write special versions of each of these.
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The following implementation uses a mix of POSIX and BSD routines. */
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#include "libgomp.h"
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#include <unistd.h>
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#include <stdlib.h>
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#ifdef HAVE_GETLOADAVG
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# ifdef HAVE_SYS_LOADAVG_H
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# include <sys/loadavg.h>
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# endif
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#endif
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#ifdef HAVE_SYS_SYSCTL_H
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# include <sys/sysctl.h>
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#endif
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static int
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get_num_procs (void)
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{
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#ifdef _SC_NPROCESSORS_ONLN
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return sysconf (_SC_NPROCESSORS_ONLN);
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#elif defined HW_NCPU
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int ncpus = 1;
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size_t len = sizeof(ncpus);
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sysctl((int[2]) {CTL_HW, HW_NCPU}, 2, &ncpus, &len, NULL, 0);
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return ncpus;
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#else
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return 0;
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#endif
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}
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/* At startup, determine the default number of threads. It would seem
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this should be related to the number of cpus online. */
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void
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gomp_init_num_threads (void)
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{
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int ncpus = get_num_procs ();
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if (ncpus > 0)
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gomp_global_icv.nthreads_var = ncpus;
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}
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/* When OMP_DYNAMIC is set, at thread launch determine the number of
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threads we should spawn for this team. */
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/* ??? I have no idea what best practice for this is. Surely some
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function of the number of processors that are *still* online and
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the load average. Here I use the number of processors online
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minus the 15 minute load average. */
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unsigned
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gomp_dynamic_max_threads (void)
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{
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unsigned n_onln, loadavg;
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unsigned nthreads_var = gomp_icv (false)->nthreads_var;
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n_onln = get_num_procs ();
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if (!n_onln || n_onln > nthreads_var)
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n_onln = nthreads_var;
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loadavg = 0;
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#ifdef HAVE_GETLOADAVG
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{
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double dloadavg[3];
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if (getloadavg (dloadavg, 3) == 3)
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{
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/* Add 0.1 to get a kind of biased rounding. */
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loadavg = dloadavg[2] + 0.1;
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}
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}
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#endif
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if (loadavg >= n_onln)
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return 1;
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else
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return n_onln - loadavg;
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}
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int
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omp_get_num_procs (void)
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{
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int ncpus = get_num_procs ();
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if (ncpus <= 0)
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ncpus = gomp_icv (false)->nthreads_var;
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return ncpus;
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}
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ialias (omp_get_num_procs)
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