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47 lines
1.6 KiB
C++
47 lines
1.6 KiB
C++
#include <Common/getNumberOfPhysicalCPUCores.h>
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#include <thread>
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#if defined(__x86_64__)
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#include <cpuid/libcpuid.h>
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#include <Common/Exception.h>
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namespace DB { namespace ErrorCodes { extern const int CPUID_ERROR; }}
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#endif
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unsigned getNumberOfPhysicalCPUCores()
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{
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#if defined(__x86_64__)
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cpu_raw_data_t raw_data;
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if (0 != cpuid_get_raw_data(&raw_data))
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throw DB::Exception("Cannot cpuid_get_raw_data: " + std::string(cpuid_error()), DB::ErrorCodes::CPUID_ERROR);
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cpu_id_t data;
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if (0 != cpu_identify(&raw_data, &data))
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throw DB::Exception("Cannot cpu_identify: " + std::string(cpuid_error()), DB::ErrorCodes::CPUID_ERROR);
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/// On Xen VMs, libcpuid returns wrong info (zero number of cores). Fallback to alternative method.
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if (data.num_logical_cpus == 0)
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return std::thread::hardware_concurrency();
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unsigned res = 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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if (res != 0)
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return res;
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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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return std::thread::hardware_concurrency();
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}
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