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/* Copyright (c) 2003-2004, Roger Dingledine
* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
* Copyright (c) 2007-2021, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file numcpus.c
* \brief Compute the number of CPUs configured on this system.
**/
#include "orconfig.h"
#include "lib/thread/numcpus.h"
#include "lib/log/log.h"
#include "lib/log/util_bug.h"
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef _WIN32
#include <windows.h>
#endif
#include <stdlib.h>
/** Implementation logic for compute_num_cpus(). */
static int
compute_num_cpus_impl(void)
{
#ifdef _WIN32
SYSTEM_INFO info;
memset(&info, 0, sizeof(info));
GetSystemInfo(&info);
if (info.dwNumberOfProcessors >= 1 && info.dwNumberOfProcessors < INT_MAX)
return (int)info.dwNumberOfProcessors;
else
return -1;
#elif defined(HAVE_SYSCONF)
#ifdef _SC_NPROCESSORS_CONF
long cpus_conf = sysconf(_SC_NPROCESSORS_CONF);
#else
long cpus_conf = -1;
#endif
#ifdef _SC_NPROCESSORS_ONLN
long cpus_onln = sysconf(_SC_NPROCESSORS_ONLN);
#else
long cpus_onln = -1;
#endif
long cpus = -1;
if (cpus_conf > 0 && cpus_onln < 0) {
cpus = cpus_conf;
} else if (cpus_onln > 0 && cpus_conf < 0) {
cpus = cpus_onln;
} else if (cpus_onln > 0 && cpus_conf > 0) {
if (cpus_onln < cpus_conf) {
log_notice(LD_GENERAL, "I think we have %ld CPUS, but only %ld of them "
"are available. Telling Tor to only use %ld. You can over"
"ride this with the NumCPUs option",
cpus_conf, cpus_onln, cpus_onln);
}
cpus = cpus_onln;
}
if (cpus >= 1 && cpus < INT_MAX)
return (int)cpus;
else
return -1;
#else
return -1;
#endif /* defined(_WIN32) || ... */
}
#define MAX_DETECTABLE_CPUS 16
/** Return how many CPUs we are running with. We assume that nobody is
* using hot-swappable CPUs, so we don't recompute this after the first
* time. Return -1 if we don't know how to tell the number of CPUs on this
* system.
*/
int
compute_num_cpus(void)
{
static int num_cpus = -2;
if (num_cpus == -2) {
num_cpus = compute_num_cpus_impl();
tor_assert(num_cpus != -2);
if (num_cpus > MAX_DETECTABLE_CPUS) {
/* LCOV_EXCL_START */
log_notice(LD_GENERAL, "Wow! I detected that you have %d CPUs. I "
"will not autodetect any more than %d, though. If you "
"want to configure more, set NumCPUs in your torrc",
num_cpus, MAX_DETECTABLE_CPUS);
num_cpus = MAX_DETECTABLE_CPUS;
/* LCOV_EXCL_STOP */
}
}
return num_cpus;
}
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