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Simplification #36313

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Alexey Milovidov 2022-04-16 02:08:06 +02:00 committed by alesapin
parent 767b2eecff
commit b6c06268eb
1 changed files with 10 additions and 24 deletions
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34
src/Common/getNumberOfPhysicalCPUCores.cpp
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@ -5,9 +5,6 @@
# include <cmath>
# include <fstream>
#endif
#if USE_CPUID
# include <libcpuid/libcpuid.h>
#endif
#include <thread>
@ -41,32 +38,21 @@ static unsigned getCGroupLimitedCPUCores(unsigned default_cpu_count)
static unsigned getNumberOfPhysicalCPUCoresImpl()
{
unsigned cpu_count = 0; // start with an invalid num
unsigned cpu_count = std::thread::hardware_concurrency();
#if USE_CPUID
cpu_raw_data_t raw_data;
cpu_id_t data;
/// Most of x86_64 CPUs have 2-way Hyper-Threading
/// Aarch64 and RISC-V don't have SMT so far.
/// 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.
/// On Xen VMs, libcpuid returns wrong info (zero number of cores). Fallback to alternative method.
/// Also, libcpuid does not support some CPUs like AMD Hygon C86 7151.
/// Also, libcpuid gives strange result on Google Compute Engine VMs.
/// Example:
/// num_cores = 12, /// number of physical cores on current CPU socket
/// total_logical_cpus = 1, /// total number of logical cores on all sockets
/// num_logical_cpus = 24. /// number of logical cores on current CPU socket
/// It means two-way hyper-threading (24 / 12), but contradictory, 'total_logical_cpus' == 1.
if (0 == cpuid_get_raw_data(&raw_data) && 0 == cpu_identify(&raw_data, &data) && data.num_logical_cpus != 0)
cpu_count = data.num_cores * data.total_logical_cpus / data.num_logical_cpus;
#if defined(__x86_64__)
/// Let's limit ourself to the number of physical cores.
/// But if the number of logical cores is small - maybe it is a small machine
/// or very limited cloud instance and it is reasonable to use all the cores.
if (cpu_count >= 8)
cpu_count /= 2;
#endif
/// As a fallback (also for non-x86 architectures) assume there are no hyper-threading on the system.
/// (Actually, only Aarch64 is supported).
if (cpu_count == 0)
cpu_count = std::thread::hardware_concurrency();
#if defined(OS_LINUX)
/// TODO: add a setting for disabling that, similar to UseContainerSupport in java
cpu_count = getCGroupLimitedCPUCores(cpu_count);
#endif