Brush up on object cache configuration

include/metall/defs.hpp

@@ -64,31 +64,60 @@
 #define METALL_DISABLE_FREE_FILE_SPACE
 #endif
 
+// --------------------
+// Macros for the segment allocator
+// --------------------
+
+#ifdef DOXYGEN_SKIP
+/// \brief If defined, 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
+
 // --------------------
 // Macros for the object cache
 // --------------------
 
-/// \def METALL_MAX_PER_CPU_CACHE_SIZE
-/// The maximum size of the per CPU (logical CPU core) cache in bytes.
-#ifndef METALL_MAX_PER_CPU_CACHE_SIZE
-#define METALL_MAX_PER_CPU_CACHE_SIZE (1ULL << 20ULL)
+#ifdef DOXYGEN_SKIP
+/// \brief If defined, Metall disables the object cache feature.
+#define METALL_DISABLE_OBJECT_CACHE
+#endif
+
+/// \def METALL_NUM_OBJECT_CACHES
+/// The total number of object caches. If this macro is defined,
+/// its value must be greater than 0.
+#ifdef DOXYGEN_SKIP
+#define METALL_NUM_OBJECT_CACHES 2
+#endif
+
+#if defined(METALL_NUM_OBJECT_CACHES) && METALL_NUM_OBJECT_CACHES <= 0
+#warning "METALL_NUM_OBJECT_CACHES must be > 0. This value is ignored."
+#undef METALL_NUM_OBJECT_CACHES
 #endif
 
 /// \def METALL_NUM_CACHES_PER_CPU
 /// The number of caches per CPU (logical CPU core).
+/// This value must be greater than 0.
+/// This macro is ignored if METALL_NUM_OBJECT_CACHES is defined.
 #ifndef METALL_NUM_CACHES_PER_CPU
 #define METALL_NUM_CACHES_PER_CPU 2
 #endif
 
-#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
+#if METALL_NUM_CACHES_PER_CPU <= 0
+#warning "METALL_NUM_CACHES_PER_CPU must be > 0."
+#undef METALL_NUM_CACHES_PER_CPU
+#define METALL_NUM_CACHES_PER_CPU 2
+#endif
+
+/// \def METALL_MAX_PER_CPU_CACHE_SIZE
+/// The maximum size of the per CPU (logical CPU core) cache in bytes.
+#ifndef METALL_MAX_PER_CPU_CACHE_SIZE
+#define METALL_MAX_PER_CPU_CACHE_SIZE (1ULL << 20ULL)
 #endif
 
 // --------------------

include/metall/kernel/object_cache.hpp

@@ -446,7 +446,7 @@ class object_cache {
   }
 
   explicit object_cache()
-      : m_num_caches(priv_get_num_cpus() * k_num_caches_per_cpu)
+      : m_num_caches(priv_get_num_cahes())
 #ifdef METALL_ENABLE_MUTEX_IN_OBJECT_CACHE
         ,
         m_mutex(m_num_caches)
@@ -544,6 +544,16 @@ class object_cache {
     return mdtl::get_num_cpus();
   }
 
+  /// Calculate the number of caches to be used.
+  inline static unsigned int priv_get_num_cahes() {
+#ifdef METALL_NUM_OBJECT_CACHES
+    if (METALL_NUM_OBJECT_CACHES > 0) {
+      return METALL_NUM_OBJECT_CACHES;
+    }
+#endif
+    return priv_get_num_cpus() * k_num_caches_per_cpu;
+  }
+
   inline size_type priv_cache_no() const {
 #ifdef METALL_DISABLE_CONCURRENCY
     return 0;