Use SettingMaxThreads only in Settings, call getNumberOfPhysicalCPUCores() instead of SettingMaxThreads::getAuto().

src/Common/ThreadPool.cpp

@@ -1,5 +1,6 @@
 #include <Common/ThreadPool.h>
 #include <Common/Exception.h>
+#include <Common/getNumberOfPhysicalCPUCores.h>
 
 #include <cassert>
 #include <type_traits>
@@ -24,6 +25,13 @@ namespace CurrentMetrics
 }
 
 
+template <typename Thread>
+ThreadPoolImpl<Thread>::ThreadPoolImpl()
+    : ThreadPoolImpl(getNumberOfPhysicalCPUCores())
+{
+}
+
+
 template <typename Thread>
 ThreadPoolImpl<Thread>::ThreadPoolImpl(size_t max_threads_)
     : ThreadPoolImpl(max_threads_, max_threads_, max_threads_)

src/Common/ThreadPool.h

@@ -29,6 +29,9 @@ class ThreadPoolImpl
 public:
     using Job = std::function<void()>;
 
+    /// Maximum number of threads is based on the number of physical cores.
+    ThreadPoolImpl();
+
     /// Size is constant. Up to num_threads are created on demand and then run until shutdown.
     explicit ThreadPoolImpl(size_t max_threads_);
 

src/Common/getNumberOfPhysicalCPUCores.cpp

@@ -9,29 +9,33 @@
 
 unsigned getNumberOfPhysicalCPUCores()
 {
-#if USE_CPUID
-    cpu_raw_data_t raw_data;
-    cpu_id_t data;
+    static const unsigned number = []
+    {
+#       if USE_CPUID
+            cpu_raw_data_t raw_data;
+            cpu_id_t data;
 
-    /// 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.
-    if (0 != cpuid_get_raw_data(&raw_data) || 0 != cpu_identify(&raw_data, &data) || data.num_logical_cpus == 0)
+            /// 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.
+            if (0 != cpuid_get_raw_data(&raw_data) || 0 != cpu_identify(&raw_data, &data) || data.num_logical_cpus == 0)
+                return std::thread::hardware_concurrency();
+
+            unsigned res = data.num_cores * data.total_logical_cpus / data.num_logical_cpus;
+
+            /// 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 (res != 0)
+                return res;
+#       endif
+
+        /// As a fallback (also for non-x86 architectures) assume there are no hyper-threading on the system.
+        /// (Actually, only Aarch64 is supported).
         return std::thread::hardware_concurrency();
-
-    unsigned res = data.num_cores * data.total_logical_cpus / data.num_logical_cpus;
-
-    /// 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 (res != 0)
-        return res;
-#endif
-
-    /// As a fallback (also for non-x86 architectures) assume there are no hyper-threading on the system.
-    /// (Actually, only Aarch64 is supported).
-    return std::thread::hardware_concurrency();
+    }();
+    return number;
 }

src/Core/SettingsCollection.cpp

@@ -210,8 +210,7 @@ void SettingMaxThreads::setAuto()
 
 UInt64 SettingMaxThreads::getAutoValue()
 {
-    static auto res = getNumberOfPhysicalCPUCores();
-    return res;
+    return getNumberOfPhysicalCPUCores();
 }
 
 

src/Databases/DatabaseOnDisk.cpp

@@ -426,7 +426,7 @@ void DatabaseOnDisk::iterateMetadataFiles(const Context & context, const Iterati
     }
 
     /// Read and parse metadata in parallel
-    ThreadPool pool(SettingMaxThreads().getAutoValue());
+    ThreadPool pool;
     for (const auto & file : metadata_files)
     {
         pool.scheduleOrThrowOnError([&]()

src/Databases/DatabaseOrdinary.cpp

@@ -152,7 +152,7 @@ void DatabaseOrdinary::loadStoredObjects(Context & context, bool has_force_resto
     std::atomic<size_t> tables_processed{0};
     std::atomic<size_t> dictionaries_processed{0};
 
-    ThreadPool pool(SettingMaxThreads().getAutoValue());
+    ThreadPool pool;
 
     /// Attach tables.
     for (const auto & name_with_query : file_names)

src/Interpreters/DatabaseCatalog.cpp

@@ -560,7 +560,7 @@ void DatabaseCatalog::loadMarkedAsDroppedTables()
         dropped_metadata.emplace(std::move(full_path), std::move(dropped_id));
     }
 
-    ThreadPool pool(SettingMaxThreads().getAutoValue());
+    ThreadPool pool;
     for (const auto & elem : dropped_metadata)
     {
         pool.scheduleOrThrowOnError([&]()