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Diffstat (limited to 'lib/nproc.c')
| -rw-r--r-- | lib/nproc.c | 404 |
1 files changed, 404 insertions, 0 deletions
diff --git a/lib/nproc.c b/lib/nproc.c new file mode 100644 index 0000000..378d3ff --- /dev/null +++ b/lib/nproc.c @@ -0,0 +1,404 @@ +/* Detect the number of processors. + + Copyright (C) 2009-2022 Free Software Foundation, Inc. + + This file 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. + + This file 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 this program. If not, see <https://www.gnu.org/licenses/>. */ + +/* Written by Glen Lenker and Bruno Haible. */ + +#include <config.h> +#include "nproc.h" + +#include <limits.h> +#include <stdlib.h> +#include <unistd.h> + +#if HAVE_PTHREAD_GETAFFINITY_NP && 0 +# include <pthread.h> +# include <sched.h> +#endif +#if HAVE_SCHED_GETAFFINITY_LIKE_GLIBC || HAVE_SCHED_GETAFFINITY_NP +# include <sched.h> +#endif + +#include <sys/types.h> + +#if HAVE_SYS_PSTAT_H +# include <sys/pstat.h> +#endif + +#if HAVE_SYS_SYSMP_H +# include <sys/sysmp.h> +#endif + +#if HAVE_SYS_PARAM_H +# include <sys/param.h> +#endif + +#if HAVE_SYS_SYSCTL_H && ! defined __GLIBC__ +# include <sys/sysctl.h> +#endif + +#if defined _WIN32 && ! defined __CYGWIN__ +# define WIN32_LEAN_AND_MEAN +# include <windows.h> +#endif + +#include "c-ctype.h" + +#include "minmax.h" + +#define ARRAY_SIZE(a) (sizeof (a) / sizeof ((a)[0])) + +/* Return the number of processors available to the current process, based + on a modern system call that returns the "affinity" between the current + process and each CPU. Return 0 if unknown or if such a system call does + not exist. */ +static unsigned long +num_processors_via_affinity_mask (void) +{ + /* glibc >= 2.3.3 with NPTL and NetBSD 5 have pthread_getaffinity_np, + but with different APIs. Also it requires linking with -lpthread. + Therefore this code is not enabled. + glibc >= 2.3.4 has sched_getaffinity whereas NetBSD 5 has + sched_getaffinity_np. */ +#if HAVE_PTHREAD_GETAFFINITY_NP && defined __GLIBC__ && 0 + { + cpu_set_t set; + + if (pthread_getaffinity_np (pthread_self (), sizeof (set), &set) == 0) + { + unsigned long count; + +# ifdef CPU_COUNT + /* glibc >= 2.6 has the CPU_COUNT macro. */ + count = CPU_COUNT (&set); +# else + size_t i; + + count = 0; + for (i = 0; i < CPU_SETSIZE; i++) + if (CPU_ISSET (i, &set)) + count++; +# endif + if (count > 0) + return count; + } + } +#elif HAVE_PTHREAD_GETAFFINITY_NP && defined __NetBSD__ && 0 + { + cpuset_t *set; + + set = cpuset_create (); + if (set != NULL) + { + unsigned long count = 0; + + if (pthread_getaffinity_np (pthread_self (), cpuset_size (set), set) + == 0) + { + cpuid_t i; + + for (i = 0;; i++) + { + int ret = cpuset_isset (i, set); + if (ret < 0) + break; + if (ret > 0) + count++; + } + } + cpuset_destroy (set); + if (count > 0) + return count; + } + } +#elif HAVE_SCHED_GETAFFINITY_LIKE_GLIBC /* glibc >= 2.3.4 */ + { + cpu_set_t set; + + if (sched_getaffinity (0, sizeof (set), &set) == 0) + { + unsigned long count; + +# ifdef CPU_COUNT + /* glibc >= 2.6 has the CPU_COUNT macro. */ + count = CPU_COUNT (&set); +# else + size_t i; + + count = 0; + for (i = 0; i < CPU_SETSIZE; i++) + if (CPU_ISSET (i, &set)) + count++; +# endif + if (count > 0) + return count; + } + } +#elif HAVE_SCHED_GETAFFINITY_NP /* NetBSD >= 5 */ + { + cpuset_t *set; + + set = cpuset_create (); + if (set != NULL) + { + unsigned long count = 0; + + if (sched_getaffinity_np (getpid (), cpuset_size (set), set) == 0) + { + cpuid_t i; + + for (i = 0;; i++) + { + int ret = cpuset_isset (i, set); + if (ret < 0) + break; + if (ret > 0) + count++; + } + } + cpuset_destroy (set); + if (count > 0) + return count; + } + } +#endif + +#if defined _WIN32 && ! defined __CYGWIN__ + { /* This works on native Windows platforms. */ + DWORD_PTR process_mask; + DWORD_PTR system_mask; + + if (GetProcessAffinityMask (GetCurrentProcess (), + &process_mask, &system_mask)) + { + DWORD_PTR mask = process_mask; + unsigned long count = 0; + + for (; mask != 0; mask = mask >> 1) + if (mask & 1) + count++; + if (count > 0) + return count; + } + } +#endif + + return 0; +} + + +/* Return the total number of processors. Here QUERY must be one of + NPROC_ALL, NPROC_CURRENT. The result is guaranteed to be at least 1. */ +static unsigned long int +num_processors_ignoring_omp (enum nproc_query query) +{ + /* On systems with a modern affinity mask system call, we have + sysconf (_SC_NPROCESSORS_CONF) + >= sysconf (_SC_NPROCESSORS_ONLN) + >= num_processors_via_affinity_mask () + The first number is the number of CPUs configured in the system. + The second number is the number of CPUs available to the scheduler. + The third number is the number of CPUs available to the current process. + + Note! On Linux systems with glibc, the first and second number come from + the /sys and /proc file systems (see + glibc/sysdeps/unix/sysv/linux/getsysstats.c). + In some situations these file systems are not mounted, and the sysconf call + returns 1 or 2 (<https://sourceware.org/bugzilla/show_bug.cgi?id=21542>), + which does not reflect the reality. */ + + if (query == NPROC_CURRENT) + { + /* Try the modern affinity mask system call. */ + { + unsigned long nprocs = num_processors_via_affinity_mask (); + + if (nprocs > 0) + return nprocs; + } + +#if defined _SC_NPROCESSORS_ONLN + { /* This works on glibc, Mac OS X 10.5, FreeBSD, AIX, OSF/1, Solaris, + Cygwin, Haiku. */ + long int nprocs = sysconf (_SC_NPROCESSORS_ONLN); + if (nprocs > 0) + return nprocs; + } +#endif + } + else /* query == NPROC_ALL */ + { +#if defined _SC_NPROCESSORS_CONF + { /* This works on glibc, Mac OS X 10.5, FreeBSD, AIX, OSF/1, Solaris, + Cygwin, Haiku. */ + long int nprocs = sysconf (_SC_NPROCESSORS_CONF); + +# if __GLIBC__ >= 2 && defined __linux__ + /* On Linux systems with glibc, this information comes from the /sys and + /proc file systems (see glibc/sysdeps/unix/sysv/linux/getsysstats.c). + In some situations these file systems are not mounted, and the + sysconf call returns 1 or 2. But we wish to guarantee that + num_processors (NPROC_ALL) >= num_processors (NPROC_CURRENT). */ + if (nprocs == 1 || nprocs == 2) + { + unsigned long nprocs_current = num_processors_via_affinity_mask (); + + if (/* nprocs_current > 0 && */ nprocs_current > nprocs) + nprocs = nprocs_current; + } +# endif + + if (nprocs > 0) + return nprocs; + } +#endif + } + +#if HAVE_PSTAT_GETDYNAMIC + { /* This works on HP-UX. */ + struct pst_dynamic psd; + if (pstat_getdynamic (&psd, sizeof psd, 1, 0) >= 0) + { + /* The field psd_proc_cnt contains the number of active processors. + In newer releases of HP-UX 11, the field psd_max_proc_cnt includes + deactivated processors. */ + if (query == NPROC_CURRENT) + { + if (psd.psd_proc_cnt > 0) + return psd.psd_proc_cnt; + } + else + { + if (psd.psd_max_proc_cnt > 0) + return psd.psd_max_proc_cnt; + } + } + } +#endif + +#if HAVE_SYSMP && defined MP_NAPROCS && defined MP_NPROCS + { /* This works on IRIX. */ + /* MP_NPROCS yields the number of installed processors. + MP_NAPROCS yields the number of processors available to unprivileged + processes. */ + int nprocs = + sysmp (query == NPROC_CURRENT && getuid () != 0 + ? MP_NAPROCS + : MP_NPROCS); + if (nprocs > 0) + return nprocs; + } +#endif + + /* Finally, as fallback, use the APIs that don't distinguish between + NPROC_CURRENT and NPROC_ALL. */ + +#if HAVE_SYSCTL && ! defined __GLIBC__ && defined HW_NCPU + { /* This works on macOS, FreeBSD, NetBSD, OpenBSD. + macOS 10.14 does not allow mib to be const. */ + int nprocs; + size_t len = sizeof (nprocs); + static int mib[][2] = { +# ifdef HW_NCPUONLINE + { CTL_HW, HW_NCPUONLINE }, +# endif + { CTL_HW, HW_NCPU } + }; + for (int i = 0; i < ARRAY_SIZE (mib); i++) + { + if (sysctl (mib[i], ARRAY_SIZE (mib[i]), &nprocs, &len, NULL, 0) == 0 + && len == sizeof (nprocs) + && 0 < nprocs) + return nprocs; + } + } +#endif + +#if defined _WIN32 && ! defined __CYGWIN__ + { /* This works on native Windows platforms. */ + SYSTEM_INFO system_info; + GetSystemInfo (&system_info); + if (0 < system_info.dwNumberOfProcessors) + return system_info.dwNumberOfProcessors; + } +#endif + + return 1; +} + +/* Parse OMP environment variables without dependence on OMP. + Return 0 for invalid values. */ +static unsigned long int +parse_omp_threads (char const* threads) +{ + unsigned long int ret = 0; + + if (threads == NULL) + return ret; + + /* The OpenMP spec says that the value assigned to the environment variables + "may have leading and trailing white space". */ + while (*threads != '\0' && c_isspace (*threads)) + threads++; + + /* Convert it from positive decimal to 'unsigned long'. */ + if (c_isdigit (*threads)) + { + char *endptr = NULL; + unsigned long int value = strtoul (threads, &endptr, 10); + + if (endptr != NULL) + { + while (*endptr != '\0' && c_isspace (*endptr)) + endptr++; + if (*endptr == '\0') + return value; + /* Also accept the first value in a nesting level, + since we can't determine the nesting level from env vars. */ + else if (*endptr == ',') + return value; + } + } + + return ret; +} + +unsigned long int +num_processors (enum nproc_query query) +{ + unsigned long int omp_env_limit = ULONG_MAX; + + if (query == NPROC_CURRENT_OVERRIDABLE) + { + unsigned long int omp_env_threads; + /* Honor the OpenMP environment variables, recognized also by all + programs that are based on OpenMP. */ + omp_env_threads = parse_omp_threads (getenv ("OMP_NUM_THREADS")); + omp_env_limit = parse_omp_threads (getenv ("OMP_THREAD_LIMIT")); + if (! omp_env_limit) + omp_env_limit = ULONG_MAX; + + if (omp_env_threads) + return MIN (omp_env_threads, omp_env_limit); + + query = NPROC_CURRENT; + } + /* Here query is one of NPROC_ALL, NPROC_CURRENT. */ + { + unsigned long nprocs = num_processors_ignoring_omp (query); + return MIN (nprocs, omp_env_limit); + } +} |