Based on a patch submitted by Jens Alfke:...

src/platform-macos.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 24 matching lines @@
 #include <mach-o/getsect.h>
 
 #include <AvailabilityMacros.h>
 
 #include <pthread.h>
 #include <semaphore.h>
 #include <signal.h>
 #include <mach/mach.h>
 #include <mach/semaphore.h>
 #include <mach/task.h>
+#include <mach/vm_statistics.h>
 #include <sys/time.h>
 #include <sys/resource.h>
 #include <sys/types.h>
 #include <stdarg.h>
 #include <stdlib.h>
 
 #include <errno.h>
 
 #undef MAP_TYPE
 
@@ skipping 61 matching lines @@
 bool OS::IsOutsideAllocatedSpace(void* address) {
   return address < lowest_ever_allocated || address >= highest_ever_allocated;
 }
 
 
 size_t OS::AllocateAlignment() {
   return getpagesize();
 }
 
 
+// Constants used for mmap.
+// kMmapFd is used to pass vm_alloc flags to tag the region with the user
+// defined tag 255 This helps identify V8-allocated regions in memory analysis
+// tools like vmmap(1).
+static const int kMmapFd = VM_MAKE_TAG(255);
+static const off_t kMmapFdOffset = 0;
+
+
 void* OS::Allocate(const size_t requested,
                    size_t* allocated,
                    bool is_executable) {
   const size_t msize = RoundUp(requested, getpagesize());
   int prot = PROT_READ | PROT_WRITE | (is_executable ? PROT_EXEC : 0);
-  void* mbase = mmap(NULL, msize, prot, MAP_PRIVATE | MAP_ANON, -1, 0);
+  void* mbase = mmap(NULL, msize, prot,
+                     MAP_PRIVATE | MAP_ANON,
+                     kMmapFd, kMmapFdOffset);
   if (mbase == MAP_FAILED) {
     LOG(StringEvent("OS::Allocate", "mmap failed"));
     return NULL;
   }
   *allocated = msize;
   UpdateAllocatedSpaceLimits(mbase, msize);
   return mbase;
 }
 
 
@@ skipping 131 matching lines @@
     frames[i].text[kStackWalkMaxTextLen - 1] = '\0';
   }
 
   DeleteArray(addresses);
   free(symbols);
 
   return frames_count;
 }
 
 
-// Constants used for mmap.
-static const int kMmapFd = -1;
-static const int kMmapFdOffset = 0;
 
 
 VirtualMemory::VirtualMemory(size_t size) {
   address_ = mmap(NULL, size, PROT_NONE,
                   MAP_PRIVATE | MAP_ANON | MAP_NORESERVE,
                   kMmapFd, kMmapFdOffset);
   size_ = size;
 }
 
 
@@ skipping 327 matching lines @@
 
   // Deallocate Mach port for thread.
   if (IsProfiling()) {
     mach_port_deallocate(data_->task_self_, data_->profiled_thread_);
   }
 }
 
 #endif  // ENABLE_LOGGING_AND_PROFILING
 
 } }  // namespace v8::internal