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100 lines
3.4 KiB
C++
100 lines
3.4 KiB
C++
#include "getNumberOfPhysicalCPUCores.h"
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#include <Common/config.h>
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#if defined(OS_LINUX)
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# include <cmath>
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# include <fstream>
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#endif
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#if USE_CPUID
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# include <libcpuid/libcpuid.h>
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#endif
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#include <thread>
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#if defined(OS_LINUX)
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unsigned getCGroupLimitedCPUCores(unsigned default_cpu_count)
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{
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// Try to look at cgroups limit if it is available.
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auto read_from = [](const char * filename, int default_value) -> int {
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std::ifstream infile(filename);
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if (!infile.is_open())
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{
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return default_value;
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}
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int idata;
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if (infile >> idata)
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return idata;
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else
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return default_value;
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};
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unsigned quota_count = default_cpu_count;
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// Return the number of milliseconds per period process is guaranteed to run.
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// -1 for no quota
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int cgroup_quota = read_from("/sys/fs/cgroup/cpu/cpu.cfs_quota_us", -1);
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int cgroup_period = read_from("/sys/fs/cgroup/cpu/cpu.cfs_period_us", -1);
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if (cgroup_quota > -1 && cgroup_period > 0)
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{
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quota_count = ceil(static_cast<float>(cgroup_quota) / static_cast<float>(cgroup_period));
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}
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// Share number (typically a number relative to 1024) (2048 typically expresses 2 CPUs worth of processing)
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// -1 for no share setup
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int cgroup_share = read_from("/sys/fs/cgroup/cpu/cpu.shares", -1);
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// Convert 1024 to no shares setup
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if (cgroup_share == 1024)
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cgroup_share = -1;
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# define PER_CPU_SHARES 1024
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unsigned share_count = default_cpu_count;
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if (cgroup_share > -1)
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{
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share_count = ceil(static_cast<float>(cgroup_share) / static_cast<float>(PER_CPU_SHARES));
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}
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return std::min(default_cpu_count, std::min(share_count, quota_count));
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}
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#endif // OS_LINUX
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unsigned getNumberOfPhysicalCPUCores()
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{
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static const unsigned number = [] {
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unsigned cpu_count = 0; // start with an invalid num
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#if USE_CPUID
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do
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{
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cpu_raw_data_t raw_data;
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cpu_id_t data;
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/// On Xen VMs, libcpuid returns wrong info (zero number of cores). Fallback to alternative method.
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/// Also, libcpuid does not support some CPUs like AMD Hygon C86 7151.
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if (0 != cpuid_get_raw_data(&raw_data) || 0 != cpu_identify(&raw_data, &data) || data.num_logical_cpus == 0)
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{
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// Just fallback
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break;
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}
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cpu_count = data.num_cores * data.total_logical_cpus / data.num_logical_cpus;
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/// Also, libcpuid gives strange result on Google Compute Engine VMs.
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/// Example:
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/// num_cores = 12, /// number of physical cores on current CPU socket
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/// total_logical_cpus = 1, /// total number of logical cores on all sockets
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/// num_logical_cpus = 24. /// number of logical cores on current CPU socket
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/// It means two-way hyper-threading (24 / 12), but contradictory, 'total_logical_cpus' == 1.
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} while (false);
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#endif
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/// As a fallback (also for non-x86 architectures) assume there are no hyper-threading on the system.
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/// (Actually, only Aarch64 is supported).
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if (cpu_count == 0)
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cpu_count = std::thread::hardware_concurrency();
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#if defined(OS_LINUX)
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cpu_count = getCGroupLimitedCPUCores(cpu_count);
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#endif // OS_LINUX
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return cpu_count;
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}();
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return number;
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}
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