Memory (macOS): updates algorithm in order not to use hw.memsize_usable which is available on newer macOS version

Adds a new CMake option to use usable memory size at the same time

Fixes #2171

CMakeLists.txt

@@ -110,6 +110,9 @@ option(ENABLE_LIBZFS "Enable libzfs" ON)
 if(WIN32 AND NOT CMAKE_SYSTEM_PROCESSOR STREQUAL "aarch64")
     option(ENABLE_WIN7_COMPAT "Enable Windows 7 compatibility" ON)
 endif()
+if(APPLE)
+    option(ENABLE_APPLE_MEMSIZE_USABLE "Use usable memory size as total memory size in Memory module, to match other systems" ON)
+endif()
 
 set(BINARY_LINK_TYPE_OPTIONS dlopen dynamic static)
 set(BINARY_LINK_TYPE dlopen CACHE STRING "How to link fastfetch")
@@ -1424,6 +1427,14 @@ elseif(GNU)
     target_compile_definitions(libfastfetch PUBLIC _GNU_SOURCE PATH_MAX=4096 O_PATH=0)
 endif()
 
+if(APPLE)
+    if(ENABLE_APPLE_MEMSIZE_USABLE)
+        target_compile_definitions(libfastfetch PUBLIC FF_APPLE_MEMSIZE_USABLE=1)
+    else()
+        target_compile_definitions(libfastfetch PUBLIC FF_APPLE_MEMSIZE_USABLE=0)
+    endif()
+endif()
+
 if(WIN32)
     check_function_exists(_msize HAVE_MSVC_MSIZE)
     if(HAVE_MSVC_MSIZE)

src/common/impl/init.c

@@ -258,6 +258,9 @@ void ffListFeatures(void)
         #if FF_WIN7_COMPAT
             "Windows 7 Compatibility\n"
         #endif
+        #if FF_APPLE_MEMSIZE_USABLE
+            "Apple memsize_usable\n"
+        #endif
         ""
     , stdout);
 }

src/detection/memory/memory_apple.c

@@ -9,30 +9,25 @@
 const char* ffDetectMemory(FFMemoryResult* ram)
 {
     size_t length = sizeof(ram->bytesTotal);
+
+    #if FF_APPLE_MEMSIZE_USABLE
+    if (sysctlbyname("hw.memsize_usable", &ram->bytesTotal, &length, NULL, 0) != 0)
+        return "Failed to read hw.memsize_usable";
+    #else
     if (sysctl((int[]){ CTL_HW, HW_MEMSIZE }, 2, &ram->bytesTotal, &length, NULL, 0) != 0)
         return "Failed to read hw.memsize";
-    uint64_t usableMemory = 0;
-    length = sizeof(usableMemory);
-    if (sysctlbyname("hw.memsize_usable", &usableMemory, &length, NULL, 0) != 0)
-        usableMemory = ram->bytesTotal;
+    #endif
 
     mach_msg_type_number_t count = HOST_VM_INFO64_COUNT;
     vm_statistics64_data_t vmstat;
     if(host_statistics64(mach_host_self(), HOST_VM_INFO64, (host_info64_t) (&vmstat), &count) != KERN_SUCCESS)
         return "Failed to read host_statistics64";
 
-    uint64_t pageSize = instance.state.platform.sysinfo.pageSize;
-    uint64_t appMemory = vmstat.internal_page_count * pageSize; // memory allocated by `mmap(..., MAP_ANON | MAP_PRIVATE, ...)`, i.e. malloc(3)
-    uint64_t wiredMemory = vmstat.wire_count * pageSize;
-    uint64_t compressed = vmstat.compressor_page_count * pageSize;
-    uint64_t reserved = ram->bytesTotal - usableMemory;
+    // https://github.com/st3fan/osx-10.9/blob/34e34a6a539b5a822cda4074e56a7ced9b57da71/system_cmds-597.1.1/vm_stat.tproj/vm_stat.c#L139
 
-    FF_DEBUG("App: %.2f GiB", (double) appMemory / 1024. / 1024. / 1024.);
-    FF_DEBUG("Wired: %.2f GiB", (double) wiredMemory / 1024. / 1024. / 1024.);
-    FF_DEBUG("Compressed: %.2f GiB", (double) compressed / 1024. / 1024. / 1024.);
-    FF_DEBUG("Reserved: %.2f GiB", (double) reserved / 1024. / 1024. / 1024.);
-
-    ram->bytesUsed = appMemory + wiredMemory + compressed + reserved;
+    uint64_t pagesFree = vmstat.free_count - vmstat.speculative_count;
+    uint64_t pagesFileBacked = vmstat.external_page_count; // Cached files
+    ram->bytesUsed = ram->bytesTotal - (pagesFree + pagesFileBacked) * instance.state.platform.sysinfo.pageSize;
 
     return NULL;
 }