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Get number of CPUs with sysconf() on Linux (#1901)

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* Get number of CPUs with sysconf() on Linux

Avoid parsing the /proc/cpuinfo just to get number of CPUs.
Instead use the portable function provided by glibc.

* Update sysinfo.cc
This commit is contained in:
Helge Deller 2025-01-09 17:07:43 +01:00 committed by GitHub
parent 39be87d300
commit c24774dc4f
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GPG Key ID: B5690EEEBB952194
1 changed files with 3 additions and 51 deletions
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54
src/sysinfo.cc
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@ -492,14 +492,14 @@ int GetNumCPUsImpl() {
GetSystemInfo(&sysinfo);
// number of logical processors in the current group
return static_cast<int>(sysinfo.dwNumberOfProcessors);
#elif defined(BENCHMARK_OS_SOLARIS)
#elif defined(__linux__) || defined(BENCHMARK_OS_SOLARIS)
// Returns -1 in case of a failure.
long num_cpu = sysconf(_SC_NPROCESSORS_ONLN);
int num_cpu = static_cast<int>(sysconf(_SC_NPROCESSORS_ONLN));
if (num_cpu < 0) {
PrintErrorAndDie("sysconf(_SC_NPROCESSORS_ONLN) failed with error: ",
strerror(errno));
}
return (int)num_cpu;
return num_cpu;
#elif defined(BENCHMARK_OS_QNX)
return static_cast<int>(_syspage_ptr->num_cpu);
#elif defined(BENCHMARK_OS_QURT)
@ -508,54 +508,6 @@ int GetNumCPUsImpl() {
hardware_threads.max_hthreads = 1;
}
return hardware_threads.max_hthreads;
#else
int num_cpus = 0;
int max_id = -1;
std::ifstream f("/proc/cpuinfo");
if (!f.is_open()) {
std::cerr << "Failed to open /proc/cpuinfo\n";
return -1;
}
#if defined(__alpha__)
const std::string Key = "cpus detected";
#else
const std::string Key = "processor";
#endif
std::string ln;
while (std::getline(f, ln)) {
if (ln.empty()) continue;
std::size_t split_idx = ln.find(':');
std::string value;
#if defined(__s390__)
// s390 has another format in /proc/cpuinfo
// it needs to be parsed differently
if (split_idx != std::string::npos)
value = ln.substr(Key.size() + 1, split_idx - Key.size() - 1);
#else
if (split_idx != std::string::npos) value = ln.substr(split_idx + 1);
#endif
if (ln.size() >= Key.size() && ln.compare(0, Key.size(), Key) == 0) {
num_cpus++;
if (!value.empty()) {
const int cur_id = benchmark::stoi(value);
max_id = std::max(cur_id, max_id);
}
}
}
if (f.bad()) {
PrintErrorAndDie("Failure reading /proc/cpuinfo");
}
if (!f.eof()) {
PrintErrorAndDie("Failed to read to end of /proc/cpuinfo");
}
f.close();
if ((max_id + 1) != num_cpus) {
fprintf(stderr,
"CPU ID assignments in /proc/cpuinfo seem messed up."
" This is usually caused by a bad BIOS.\n");
}
return num_cpus;
#endif
BENCHMARK_UNREACHABLE();
}