mirror of
https://github.com/ClickHouse/ClickHouse.git
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68 lines
2.0 KiB
C++
68 lines
2.0 KiB
C++
#include "getNumberOfPhysicalCPUCores.h"
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#include "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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#include <thread>
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#if defined(OS_LINUX)
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static int32_t readFrom(const char * filename, int default_value)
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{
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std::ifstream infile(filename);
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if (!infile.is_open())
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return default_value;
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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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/// Try to look at cgroups limit if it is available.
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static uint32_t getCGroupLimitedCPUCores(unsigned default_cpu_count)
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{
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uint32_t 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 = readFrom("/sys/fs/cgroup/cpu/cpu.cfs_quota_us", -1);
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int cgroup_period = readFrom("/sys/fs/cgroup/cpu/cpu.cfs_period_us", -1);
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if (cgroup_quota > -1 && cgroup_period > 0)
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quota_count = static_cast<uint32_t>(ceil(static_cast<float>(cgroup_quota) / static_cast<float>(cgroup_period)));
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return std::min(default_cpu_count, quota_count);
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}
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#endif
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static unsigned getNumberOfPhysicalCPUCoresImpl()
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{
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unsigned cpu_count = std::thread::hardware_concurrency();
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/// Most of x86_64 CPUs have 2-way Hyper-Threading
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/// Aarch64 and RISC-V don't have SMT so far.
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/// POWER has SMT and it can be multiple way (like 8-way), but we don't know how ClickHouse really behaves, so use all of them.
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#if defined(__x86_64__)
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/// Let's limit ourself to the number of physical cores.
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/// But if the number of logical cores is small - maybe it is a small machine
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/// or very limited cloud instance and it is reasonable to use all the cores.
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if (cpu_count >= 32)
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cpu_count /= 2;
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#endif
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#if defined(OS_LINUX)
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cpu_count = getCGroupLimitedCPUCores(cpu_count);
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#endif
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return cpu_count;
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}
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unsigned getNumberOfPhysicalCPUCores()
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{
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/// Calculate once.
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static auto res = getNumberOfPhysicalCPUCoresImpl();
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return res;
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}
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