--- Source/WTF/wtf/RAMSize.cpp.orig	2019-10-14 22:59:02.000000000 -0700
+++ Source/WTF/wtf/RAMSize.cpp	2019-10-14 23:02:19.000000000 -0700
@@ -29,6 +29,15 @@
 #include <mutex>
 #include <wtf/StdLibExtras.h>
 
+#if OS(DARWIN)
+#import <dispatch/dispatch.h>
+#import <mach/host_info.h>
+#import <mach/mach.h>
+#import <mach/mach_error.h>
+#import <math.h>
+static const size_t ramSizeGuess = 512 * MB;
+#else
+
 #if OS(WINDOWS)
 #include <windows.h>
 #elif defined(USE_SYSTEM_MALLOC) && USE_SYSTEM_MALLOC
@@ -39,6 +47,8 @@
 #include <bmalloc/bmalloc.h>
 #endif
 
+#endif //OS(DARWIN)
+
 namespace WTF {
 
 #if OS(WINDOWS)
@@ -47,6 +57,29 @@
 
 static size_t computeRAMSize()
 {
+#if OS(DARWIN)
+    host_basic_info_data_t hostInfo;
+
+    mach_port_t host = mach_host_self();
+    mach_msg_type_number_t count = HOST_BASIC_INFO_COUNT;
+    kern_return_t r = host_info(host, HOST_BASIC_INFO, (host_info_t)&hostInfo, &count);
+    mach_port_deallocate(mach_task_self(), host);
+    if (r != KERN_SUCCESS) {
+        LOG_ERROR("%s : host_info(%d) : %s.\n", __FUNCTION__, r, mach_error_string(r));
+        return ramSizeGuess;
+    }
+
+    if (hostInfo.max_mem > std::numeric_limits<size_t>::max())
+        return std::numeric_limits<size_t>::max();
+
+    size_t sizeAccordingToKernel = static_cast<size_t>(hostInfo.max_mem);
+    size_t multiple = 128 * MB;
+
+    // Round up the memory size to a multiple of 128MB because max_mem may not be exactly 512MB
+    // (for example) and we have code that depends on those boundaries.
+    return ((sizeAccordingToKernel + multiple - 1) / multiple) * multiple;
+#else
+
 #if OS(WINDOWS)
     MEMORYSTATUSEX status;
     status.dwLength = sizeof(status);
@@ -65,6 +98,9 @@
 #else
     return bmalloc::api::availableMemory();
 #endif
+
+#endif //OS(DARWIN)
+
 }
 
 size_t ramSize()