[WIP] Add SharedMemoryTracker to dump base::SharedMemory usage

base/memory/shared_memory_mac.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/memory/shared_memory.h"
 
 #include <errno.h>
 #include <mach/mach_vm.h>
 #include <stddef.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <unistd.h>
 
 #include "base/files/file_util.h"
 #include "base/files/scoped_file.h"
 #include "base/logging.h"
 #include "base/mac/mac_util.h"
 #include "base/mac/scoped_mach_vm.h"
 #include "base/memory/shared_memory_helper.h"
+#include "base/memory/shared_memory_tracker.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/posix/safe_strerror.h"
 #include "base/process/process_metrics.h"
 #include "base/scoped_generic.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_restrictions.h"
 #include "build/build_config.h"
 
@@ skipping 175 matching lines @@
     return false;
   if (memory_)
     return false;
 
   bool success = shm_.MapAt(offset, bytes, &memory_, read_only_);
   if (success) {
     mapped_size_ = bytes;
     DCHECK_EQ(0U, reinterpret_cast<uintptr_t>(memory_) &
                       (SharedMemory::MAP_MINIMUM_ALIGNMENT - 1));
     mapped_memory_mechanism_ = shm_.type_;
+    SharedMemoryTracker::GetInstance()->IncrementMemoryUsage(*this);
   } else {
     memory_ = NULL;
   }
 
   return success;
 }
 
 bool SharedMemory::Unmap() {
   if (memory_ == NULL)
     return false;
 
   switch (mapped_memory_mechanism_) {
     case SharedMemoryHandle::POSIX:
       munmap(memory_, mapped_size_);
       break;
     case SharedMemoryHandle::MACH:
       mach_vm_deallocate(mach_task_self(),
                          reinterpret_cast<mach_vm_address_t>(memory_),
                          mapped_size_);
       break;
   }
-
+  SharedMemoryTracker::GetInstance()->DecrementMemoryUsage(*this);
   memory_ = NULL;
   mapped_size_ = 0;
   return true;
 }
 
 SharedMemoryHandle SharedMemory::handle() const {
   switch (shm_.type_) {
     case SharedMemoryHandle::POSIX:
       return SharedMemoryHandle(
           FileDescriptor(shm_.file_descriptor_.fd, false));
     case SharedMemoryHandle::MACH:
       return shm_;
   }
 }
 
 SharedMemoryHandle SharedMemory::TakeHandle() {
   SharedMemoryHandle dup = DuplicateHandle(handle());
   Close();
   return dup;
 }
 
 void SharedMemory::Close() {
+  SharedMemoryTracker::GetInstance()->DecrementMemoryUsage(*this);

[Primiano Tucci (use gerrit), 2017/01/20 16:34:52]

I think this might not be the right point.
The decription of SharedMemory::Close()  says:
// Closes the open shared memory segment. The memory will remain mapped if
// it was previously mapped.
// It is safe to call Close repeatedly.

In other words, if you Map() and then Close(), you are still using memory. Close
just frees up the file descriptor.
I believe that what you want to intercept here is the SharedMemory::Unmap()

[hajimehoshi, 2017/01/23 11:59:09]

I was wondering if the file descriptor's is still usable for ID even after
closing.

Anyway you are right that Close doesn't affect memory usage. Done.

   shm_.Close();
   shm_ = SharedMemoryHandle();
   if (shm_.type_ == SharedMemoryHandle::POSIX) {
     if (readonly_mapped_file_ > 0) {
       if (IGNORE_EINTR(close(readonly_mapped_file_)) < 0)
         PLOG(ERROR) << "close";
       readonly_mapped_file_ = -1;
     }
   }
 }
@@ skipping 50 matching lines @@
                                         ShareMode share_mode) {
   bool success = Share(new_handle, share_mode);
   if (close_self) {
     Unmap();
     Close();
   }
   return success;
 }
 
 }  // namespace base