File size: 2,536 Bytes
57c2394 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 | #include "cpu_threads.h"
#include <algorithm>
#include <cstdlib>
#include <fstream>
#include <set>
#include <string>
#include <thread>
#include <utility>
#if defined(__APPLE__)
#include <sys/sysctl.h>
#endif
#if defined(__linux__)
#include <sched.h>
#endif
namespace orbitquant::cpu {
namespace {
int environment_thread_count() {
char const *value = std::getenv("ORBITQUANT_CPU_THREADS");
if (value == nullptr) {
value = std::getenv("OMP_NUM_THREADS");
}
if (value == nullptr) {
return 0;
}
char *end = nullptr;
const long parsed = std::strtol(value, &end, 10);
if (end == value || parsed <= 0) {
return 0;
}
return static_cast<int>(std::min<long>(parsed, 64));
}
#if defined(__linux__)
int affinity_physical_core_count() {
cpu_set_t affinity;
CPU_ZERO(&affinity);
if (sched_getaffinity(0, sizeof(affinity), &affinity) != 0) {
return 0;
}
int logical_cpus = 0;
std::set<std::pair<int, int>> physical_cores;
for (int cpu = 0; cpu < CPU_SETSIZE; ++cpu) {
if (!CPU_ISSET(cpu, &affinity)) {
continue;
}
++logical_cpus;
int package = -1;
int core = -1;
std::ifstream package_file(
"/sys/devices/system/cpu/cpu" + std::to_string(cpu) +
"/topology/physical_package_id");
std::ifstream core_file(
"/sys/devices/system/cpu/cpu" + std::to_string(cpu) +
"/topology/core_id");
if (package_file >> package && core_file >> core) {
physical_cores.emplace(package, core);
}
}
return physical_cores.empty()
? logical_cpus
: static_cast<int>(physical_cores.size());
}
#endif
int default_thread_count() {
#if defined(__APPLE__)
int performance_cores = 0;
std::size_t size = sizeof(performance_cores);
if (sysctlbyname(
"hw.perflevel0.physicalcpu",
&performance_cores,
&size,
nullptr,
0) == 0 &&
performance_cores > 0) {
return std::min(performance_cores, 64);
}
#endif
#if defined(__linux__)
const int affinity_cores = affinity_physical_core_count();
if (affinity_cores > 0) {
return std::min(affinity_cores, 64);
}
#endif
const unsigned hardware = std::thread::hardware_concurrency();
return static_cast<int>(hardware == 0 ? 1 : std::min<unsigned>(hardware, 64));
}
} // namespace
int requested_threads() {
const int environment = environment_thread_count();
static const int default_threads = default_thread_count();
return environment > 0 ? environment : default_threads;
}
} // namespace orbitquant::cpu
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