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

@@ -8,6 +8,8 @@
 
 
 unsigned getNumberOfPhysicalCPUCores()
+{
+    static const unsigned number = []
     {
 #       if USE_CPUID
             cpu_raw_data_t raw_data;
@@ -34,4 +36,6 @@ unsigned getNumberOfPhysicalCPUCores()
         /// 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([&]()