Tag Mac VM regions allocated by V8. This has no effect other than making it possi...

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 66 matching lines @@
 size_t OS::AllocateAlignment() {
   return getpagesize();
 }
 
 
 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);
+  // Use the fd parameter 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).
+  void* mbase = mmap(NULL, msize, prot,
+                     MAP_PRIVATE | MAP_ANON,
+                     VM_MAKE_TAG(255), 0);
   if (mbase == MAP_FAILED) {
     LOG(StringEvent("OS::Allocate", "mmap failed"));
     return NULL;
   }
   *allocated = msize;
   UpdateAllocatedSpaceLimits(mbase, msize);
   return mbase;
 }
 
 
@@ skipping 46 matching lines @@
   void* memory_;
   int size_;
 };
 
 
 OS::MemoryMappedFile* OS::MemoryMappedFile::create(const char* name, int size,
     void* initial) {
   FILE* file = fopen(name, "w+");
   if (file == NULL) return NULL;
   fwrite(initial, size, 1, file);
-  void* memory =
-      mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, fileno(file), 0);
+  void* memory = mmap(0, size, PROT_READ | PROT_WRITE,
+                      MAP_SHARED,
+                      fileno(file), 0);
   return new PosixMemoryMappedFile(file, memory, size);
 }
 
 
 PosixMemoryMappedFile::~PosixMemoryMappedFile() {
   if (memory_) munmap(memory_, size_);
   fclose(file_);
 }
 
 
@@ skipping 63 matching lines @@
     frames[i].text[kStackWalkMaxTextLen - 1] = '\0';
   }
 
   DeleteArray(addresses);
   free(symbols);
 
   return frames_count;
 }
 
 
-// Constants used for mmap.
-static const int kMmapFd = -1;
+// Constants used for mmap calls by the VirtualMemory class.
+// kMmapFd is used to pass vm_alloc flags to tag the region with the user
+// defined tag 254. This helps identify V8-allocated regions in memory analysis
+// tools like vmmap(1).
+static const int kMmapFlags = MAP_PRIVATE | MAP_ANON;
+static const int kMmapFd = VM_MAKE_TAG(254);
 static const int kMmapFdOffset = 0;
 
 
 VirtualMemory::VirtualMemory(size_t size) {
   address_ = mmap(NULL, size, PROT_NONE,
-                  MAP_PRIVATE | MAP_ANON | MAP_NORESERVE,
+                  kMmapFlags | MAP_NORESERVE,
                   kMmapFd, kMmapFdOffset);
   size_ = size;
 }
 
 
 VirtualMemory::~VirtualMemory() {
   if (IsReserved()) {
     if (0 == munmap(address(), size())) address_ = MAP_FAILED;
   }
 }
 
 
 bool VirtualMemory::IsReserved() {
   return address_ != MAP_FAILED;
 }
 
 
 bool VirtualMemory::Commit(void* address, size_t size, bool is_executable) {
   int prot = PROT_READ | PROT_WRITE | (is_executable ? PROT_EXEC : 0);
   if (MAP_FAILED == mmap(address, size, prot,
-                         MAP_PRIVATE | MAP_ANON | MAP_FIXED,
+                         kMmapFlags | MAP_FIXED,
                          kMmapFd, kMmapFdOffset)) {
     return false;
   }
 
   UpdateAllocatedSpaceLimits(address, size);
   return true;
 }
 
 
 bool VirtualMemory::Uncommit(void* address, size_t size) {
   return mmap(address, size, PROT_NONE,
-              MAP_PRIVATE | MAP_ANON | MAP_NORESERVE | MAP_FIXED,
+              kMmapFlags | MAP_NORESERVE | MAP_FIXED,
               kMmapFd, kMmapFdOffset) != MAP_FAILED;
 }
 
 
 class ThreadHandle::PlatformData : public Malloced {
  public:
   explicit PlatformData(ThreadHandle::Kind kind) {
     Initialize(kind);
   }
 
@@ skipping 289 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