diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7b268253..16c14325 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -101,10 +101,6 @@ set(INITIAL_SEGMENT_SIZE "0" CACHE STRING
         "Set the initial segment size (use the internally defined value if 0 is specified)")
 
 # ---------- Experimental options ---------- #
-# This mode still uses multiple threads inside Metall.
-# However, applications must not use metall with multiple threads.
-option(SINGLE_THREAD_ALLOC "Optimize Metall kernel for single thread usage" OFF)
-
 option(USE_ANONYMOUS_NEW_MAP "Use the anonymous map when creating a new map region" OFF)
 set(UMAP_ROOT "" CACHE PATH "UMap installed root directory")
 
@@ -215,11 +211,6 @@ if (USE_ANONYMOUS_NEW_MAP)
     message(STATUS "Use the anonymous map for new map region")
 endif ()
 
-if (SINGLE_THREAD_ALLOC)
-    list(APPEND METALL_DEFS "METALL_SINGLE_THREAD_ALLOC")
-    message(STATUS "Optimize Metall kernel for single thread usage")
-endif ()
-
 # Requirements for GCC
 if (NOT RUN_BUILD_AND_TEST_WITH_CI)
     if (("${CMAKE_C_COMPILER_ID}" STREQUAL "GNU") OR ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU"))
diff --git a/include/metall/basic_manager.hpp b/include/metall/basic_manager.hpp
index fb18ca9f..8b9c3066 100644
--- a/include/metall/basic_manager.hpp
+++ b/include/metall/basic_manager.hpp
@@ -6,6 +6,17 @@
 #ifndef METALL_BASIC_MANAGER_HPP
 #define METALL_BASIC_MANAGER_HPP
 
+#ifdef DOXYGEN_SKIP
+/// \brief A macro to disable concurrency support.
+/// \details
+/// If this macro is defined, Metall disables concurrency support and optimizes
+/// the internal behavior for single-thread usage. Applications must not call
+/// any Metall functions concurrently if this macro is defined. On the other
+/// hand, Metall still may use multi-threading for internal operations, such
+/// as synchronizing data with files.
+#define METALL_DISABLE_CONCURRENCY
+#endif
+
 #include <cstddef>
 #include <memory>
 
diff --git a/include/metall/kernel/manager_kernel.hpp b/include/metall/kernel/manager_kernel.hpp
index f5ca062b..04ab6391 100644
--- a/include/metall/kernel/manager_kernel.hpp
+++ b/include/metall/kernel/manager_kernel.hpp
@@ -43,8 +43,10 @@
 #include <metall/kernel/segment_storage/mmap_segment_storage.hpp>
 #endif
 
-#define ENABLE_MUTEX_IN_METALL_MANAGER_KERNEL 1
-#if ENABLE_MUTEX_IN_METALL_MANAGER_KERNEL
+#ifndef METALL_DISABLE_CONCURRENCY
+#define METALL_ENABLE_MUTEX_IN_MANAGER_KERNEL
+#endif
+#ifdef METALL_ENABLE_MUTEX_IN_MANAGER_KERNEL
 #include <metall/detail/mutex.hpp>
 #endif
 
@@ -140,7 +142,7 @@ class manager_kernel {
 
   using json_store = mdtl::ptree::node_type;
 
-#if ENABLE_MUTEX_IN_METALL_MANAGER_KERNEL
+#ifdef METALL_ENABLE_MUTEX_IN_MANAGER_KERNEL
   using mutex_type = mdtl::mutex;
   using lock_guard_type = mdtl::mutex_lock_guard;
 #endif
@@ -596,7 +598,7 @@ class manager_kernel {
   segment_memory_allocator m_segment_memory_allocator{nullptr};
   std::unique_ptr<json_store> m_manager_metadata{nullptr};
 
-#if ENABLE_MUTEX_IN_METALL_MANAGER_KERNEL
+#ifdef METALL_ENABLE_MUTEX_IN_MANAGER_KERNEL
   std::unique_ptr<mutex_type> m_object_directories_mutex{nullptr};
 #endif
 };
diff --git a/include/metall/kernel/manager_kernel_impl.ipp b/include/metall/kernel/manager_kernel_impl.ipp
index 6f4eaa20..2d9f7641 100644
--- a/include/metall/kernel/manager_kernel_impl.ipp
+++ b/include/metall/kernel/manager_kernel_impl.ipp
@@ -21,7 +21,7 @@ manager_kernel<chnk_no, chnk_sz>::manager_kernel()
   if (!m_manager_metadata) {
     return;
   }
-#if ENABLE_MUTEX_IN_METALL_MANAGER_KERNEL
+#ifdef METALL_ENABLE_MUTEX_IN_MANAGER_KERNEL
   m_object_directories_mutex = std::make_unique<mutex_type>();
   if (!m_object_directories_mutex) {
     return;
@@ -177,7 +177,7 @@ bool manager_kernel<chnk_no, chnk_sz>::destroy(char_ptr_holder_type name) {
   size_type length = 0;
 
   {
-#if ENABLE_MUTEX_IN_METALL_MANAGER_KERNEL
+#ifdef METALL_ENABLE_MUTEX_IN_MANAGER_KERNEL
     lock_guard_type guard(*m_object_directories_mutex);
 #endif
 
@@ -204,7 +204,7 @@ bool manager_kernel<chnk_no, chnk_sz>::destroy_ptr(const T *ptr) {
 
   size_type length = 0;
   {
-#if ENABLE_MUTEX_IN_METALL_MANAGER_KERNEL
+#ifdef METALL_ENABLE_MUTEX_IN_MANAGER_KERNEL
     lock_guard_type guard(*m_object_directories_mutex);
 #endif
 
@@ -820,7 +820,7 @@ T *manager_kernel<chnk_no, chnk_sz>::priv_generic_construct(
 
   void *ptr = nullptr;
   try {
-#if ENABLE_MUTEX_IN_METALL_MANAGER_KERNEL
+#ifdef METALL_ENABLE_MUTEX_IN_MANAGER_KERNEL
     lock_guard_type guard(*m_object_directories_mutex);
 #endif
 
@@ -856,7 +856,7 @@ T *manager_kernel<chnk_no, chnk_sz>::priv_generic_construct(
       ptr, [this](void *const ptr) {
         try {
           {
-#if ENABLE_MUTEX_IN_METALL_MANAGER_KERNEL
+#ifdef METALL_ENABLE_MUTEX_IN_MANAGER_KERNEL
             lock_guard_type guard(*m_object_directories_mutex);
 #endif
             priv_remove_attr_object_no_mutex(priv_to_offset(ptr));
diff --git a/include/metall/kernel/object_cache.hpp b/include/metall/kernel/object_cache.hpp
index 4c2890a0..0d84f706 100644
--- a/include/metall/kernel/object_cache.hpp
+++ b/include/metall/kernel/object_cache.hpp
@@ -20,12 +20,12 @@
 #include <metall/detail/proc.hpp>
 #include <metall/detail/hash.hpp>
 
-#ifndef METALL_SINGLE_THREAD_ALLOC
+#ifndef METALL_DISABLE_CONCURRENCY
 #define METALL_ENABLE_MUTEX_IN_OBJECT_CACHE
+#endif
 #ifdef METALL_ENABLE_MUTEX_IN_OBJECT_CACHE
 #include <metall/detail/mutex.hpp>
 #endif
-#endif
 
 namespace metall::kernel {
 
@@ -58,7 +58,7 @@ class object_cache {
   // -------------------- //
 
   static constexpr std::size_t k_num_cache_per_core =
-#ifdef METALL_SINGLE_THREAD_ALLOC
+#ifdef METALL_DISABLE_CONCURRENCY
       1;
 #else
       4;
@@ -232,7 +232,7 @@ class object_cache {
   }
 
   std::size_t priv_comp_cache_no() const {
-#ifdef METALL_SINGLE_THREAD_ALLOC
+#ifdef METALL_DISABLE_CONCURRENCY
     return 0;
 #endif
 #if SUPPORT_GET_CPU_CORE_NO
@@ -252,7 +252,7 @@ class object_cache {
   /// \brief Get CPU core number.
   /// This function does not call the system call every time as it is slow.
   static std::size_t priv_get_core_no() {
-#ifdef METALL_SINGLE_THREAD_ALLOC
+#ifdef METALL_DISABLE_CONCURRENCY
         return 0;
 #endif
     thread_local static int cached_core_no = 0;
@@ -265,7 +265,7 @@ class object_cache {
   }
 
   static std::size_t get_num_cores() {
-#ifdef METALL_SINGLE_THREAD_ALLOC
+#ifdef METALL_DISABLE_CONCURRENCY
     return 1;
 #else
     return std::thread::hardware_concurrency();
diff --git a/include/metall/kernel/segment_allocator.hpp b/include/metall/kernel/segment_allocator.hpp
index 08afc38d..a92895cd 100644
--- a/include/metall/kernel/segment_allocator.hpp
+++ b/include/metall/kernel/segment_allocator.hpp
@@ -24,8 +24,11 @@
 #include <metall/detail/utilities.hpp>
 #include <metall/logger.hpp>
 
-#define ENABLE_MUTEX_IN_METALL_SEGMENT_ALLOCATOR 1
-#if ENABLE_MUTEX_IN_METALL_SEGMENT_ALLOCATOR
+#ifndef METALL_DISABLE_CONCURRENCY
+#define METALL_ENABLE_MUTEX_IN_SEGMENT_ALLOCATOR
+#endif
+
+#ifdef METALL_ENABLE_MUTEX_IN_SEGMENT_ALLOCATOR
 #include <metall/detail/mutex.hpp>
 #endif
 
@@ -94,7 +97,7 @@ class segment_allocator {
                    myself>;
 #endif
 
-#if ENABLE_MUTEX_IN_METALL_SEGMENT_ALLOCATOR
+#ifdef METALL_ENABLE_MUTEX_IN_SEGMENT_ALLOCATOR
   using mutex_type = mdtl::mutex;
   using lock_guard_type = mdtl::mutex_lock_guard;
 #endif
@@ -114,13 +117,13 @@ class segment_allocator {
         ,
         m_object_cache()
 #endif
-#if ENABLE_MUTEX_IN_METALL_SEGMENT_ALLOCATOR
+#ifdef METALL_ENABLE_MUTEX_IN_SEGMENT_ALLOCATOR
         ,
         m_chunk_mutex(nullptr),
         m_bin_mutex(nullptr)
 #endif
   {
-#if ENABLE_MUTEX_IN_METALL_SEGMENT_ALLOCATOR
+#ifdef METALL_ENABLE_MUTEX_IN_SEGMENT_ALLOCATOR
     m_chunk_mutex = std::make_unique<mutex_type>();
     m_bin_mutex = std::make_unique<std::array<mutex_type, k_num_small_bins>>();
 #endif
@@ -217,7 +220,7 @@ class segment_allocator {
   /// This function is not cheap if many objects are allocated.
   /// \return Returns true if all memory is deallocated.
   bool all_memory_deallocated() const {
-#if ENABLE_MUTEX_IN_METALL_SEGMENT_ALLOCATOR
+#ifdef METALL_ENABLE_MUTEX_IN_SEGMENT_ALLOCATOR
     lock_guard_type chunk_guard(*m_chunk_mutex);
 #endif
 
@@ -384,7 +387,7 @@ class segment_allocator {
   void priv_allocate_small_objects_from_global(
       const bin_no_type bin_no, const size_type num_allocates,
       difference_type *const allocated_offsets) {
-#if ENABLE_MUTEX_IN_METALL_SEGMENT_ALLOCATOR
+#ifdef METALL_ENABLE_MUTEX_IN_SEGMENT_ALLOCATOR
     lock_guard_type bin_guard(m_bin_mutex->at(bin_no));
 #endif
 
@@ -470,7 +473,7 @@ class segment_allocator {
 
   bool priv_insert_new_small_object_chunk(const bin_no_type bin_no) {
     chunk_no_type new_chunk_no;
-#if ENABLE_MUTEX_IN_METALL_SEGMENT_ALLOCATOR
+#ifdef METALL_ENABLE_MUTEX_IN_SEGMENT_ALLOCATOR
     lock_guard_type chunk_guard(*m_chunk_mutex);
 #endif
     new_chunk_no = m_chunk_directory.insert(bin_no);
@@ -482,7 +485,7 @@ class segment_allocator {
   }
 
   difference_type priv_allocate_large_object(const bin_no_type bin_no) {
-#if ENABLE_MUTEX_IN_METALL_SEGMENT_ALLOCATOR
+#ifdef METALL_ENABLE_MUTEX_IN_SEGMENT_ALLOCATOR
     lock_guard_type chunk_guard(*m_chunk_mutex);
 #endif
     const chunk_no_type new_chunk_no = m_chunk_directory.insert(bin_no);
@@ -535,7 +538,7 @@ class segment_allocator {
   void priv_deallocate_small_objects_from_global(
       const bin_no_type bin_no, const size_type num_deallocates,
       const difference_type offsets[]) {
-#if ENABLE_MUTEX_IN_METALL_SEGMENT_ALLOCATOR
+#ifdef METALL_ENABLE_MUTEX_IN_SEGMENT_ALLOCATOR
     lock_guard_type bin_guard(m_bin_mutex->at(bin_no));
 #endif
     for (size_type i = 0; i < num_deallocates; ++i) {
@@ -559,7 +562,7 @@ class segment_allocator {
     } else if (m_chunk_directory.all_slots_unmarked(chunk_no)) {
       // All slots in the chunk are not used, deallocate it
       {
-#if ENABLE_MUTEX_IN_METALL_SEGMENT_ALLOCATOR
+#ifdef METALL_ENABLE_MUTEX_IN_SEGMENT_ALLOCATOR
         lock_guard_type chunk_guard(*m_chunk_mutex);
 #endif
         m_chunk_directory.erase(chunk_no);
@@ -639,7 +642,7 @@ class segment_allocator {
 
   void priv_deallocate_large_object(const chunk_no_type chunk_no,
                                     const bin_no_type bin_no) {
-#if ENABLE_MUTEX_IN_METALL_SEGMENT_ALLOCATOR
+#ifdef METALL_ENABLE_MUTEX_IN_SEGMENT_ALLOCATOR
     lock_guard_type chunk_guard(*m_chunk_mutex);
 #endif
     m_chunk_directory.erase(chunk_no);
@@ -717,7 +720,7 @@ class segment_allocator {
   small_object_cache_type m_object_cache;
 #endif
 
-#if ENABLE_MUTEX_IN_METALL_SEGMENT_ALLOCATOR
+#ifdef METALL_ENABLE_MUTEX_IN_SEGMENT_ALLOCATOR
   std::unique_ptr<mutex_type> m_chunk_mutex{nullptr};
   std::unique_ptr<std::array<mutex_type, k_num_small_bins>> m_bin_mutex{
       nullptr};
diff --git a/test/kernel/CMakeLists.txt b/test/kernel/CMakeLists.txt
index ee042dd8..6f2c75a2 100644
--- a/test/kernel/CMakeLists.txt
+++ b/test/kernel/CMakeLists.txt
@@ -11,7 +11,7 @@ add_metall_test_executable(chunk_directory_test chunk_directory_test.cpp)
 add_metall_test_executable(manager_test manager_test.cpp)
 
 add_metall_test_executable(manager_test_single_thread manager_test.cpp)
-target_compile_definitions(manager_test_single_thread PRIVATE METALL_SINGLE_THREAD_ALLOC)
+target_compile_definitions(manager_test_single_thread PRIVATE METALL_DISABLE_CONCURRENCY)
 
 add_metall_test_executable(snapshot_test snapshot_test.cpp)