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

base/memory/shared_memory_tracker.cc

+// Copyright 2017 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_tracker.h"
+
+#include "base/memory/shared_memory.h"
+#include "base/strings/stringprintf.h"
+#include "base/trace_event/memory_dump_manager.h"
+#include "base/trace_event/process_memory_dump.h"
+
+namespace base {
+
+const char* kSharedMemoryDumpName = "sharedmemory";

[ssid, 2017/01/24 04:39:50]

shared_memory? other dump provider add names with '_'.

+
+SharedMemoryTracker* SharedMemoryTracker::GetInstance() {
+  return base::Singleton<SharedMemoryTracker, base::LeakySingletonTraits<
+                                                  SharedMemoryTracker>>::get();
+}
+
+bool SharedMemoryTracker::AddOwnershipEdgeToSharedGlobalDump(

[ssid, 2017/01/24 04:39:50]

I think this should be changed to:
SharedMemoryTracker::AddSuballocation(
    trace_event::ProcessMemoryDump* pmd,
    const trace_event::MemoryAllocatorDumpGuid& source,
    const SharedMemoryHandle& shared_memory_handle,
    size_t mapped_size) {
  auto* in_process_dump_name = base::StringPrintf("%s/%s",
kSharedMemoryDumpName, id_str.c_str());
  pmd->AddSubalocation(source, in_process_dump_name);
}

I am assuming that the mapped_size is not same as the size of the dump given by
line 57 in this file (usage.second).


In case if the usage.second is same as the mapped_size always, then this
function should be:
SharedMemoryTracker::AddOwnershipEdge(
    trace_event::ProcessMemoryDump* pmd,
    const trace_event::MemoryAllocatorDumpGuid& source,
    const SharedMemoryHandle& shared_memory_handle) {
  pmd->AddOwnershipEdge(source,
      base::trace_event::MemoryAllocatorDumpGuid(dump_name));
}

+    trace_event::ProcessMemoryDump* pmd,
+    const trace_event::MemoryAllocatorDumpGuid& source,
+    const SharedMemoryHandle& shared_memory_handle,
+    size_t mapped_size) {
+  SharedMemoryHandleID id;
+  if (!GetIDFromSharedMemoryHandle(shared_memory_handle, &id)) {
+    return false;
+  }
+  std::string id_str = GetSharedMemoryHandleIDString(id);
+  std::string dump_name =
+      base::StringPrintf("%s/%s", kSharedMemoryDumpName, id_str.c_str());
+  auto global_dump = pmd->CreateSharedGlobalAllocatorDump(
+      base::trace_event::MemoryAllocatorDumpGuid(dump_name));
+  global_dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
+                         base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+                         mapped_size);
+  pmd->AddOwnershipEdge(source, global_dump->guid());
+  return true;
+}
+
+bool SharedMemoryTracker::OnMemoryDump(
+    const base::trace_event::MemoryDumpArgs& args,
+    base::trace_event::ProcessMemoryDump* pmd) {
+  for (auto& bucket : buckets_) {
+    base::AutoLock lock(bucket.lock);
+    for (const auto& usage : bucket.usages) {
+      SharedMemoryHandleID id = usage.first;
+      std::string id_str = GetSharedMemoryHandleIDString(id);
+      std::string dump_name =
+          base::StringPrintf("%s/%s", kSharedMemoryDumpName, id_str.c_str());
+      auto guid = base::trace_event::MemoryAllocatorDumpGuid(dump_name);
+      base::trace_event::MemoryAllocatorDump* local_dump =
+          pmd->CreateAllocatorDump(dump_name);
+      local_dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
+                            base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+                            usage.second);
+      base::trace_event::MemoryAllocatorDump* global_dump =
+          pmd->CreateSharedGlobalAllocatorDump(guid);
+      global_dump->AddScalar(
+          base::trace_event::MemoryAllocatorDump::kNameSize,
+          base::trace_event::MemoryAllocatorDump::kUnitsBytes, usage.second);
+      pmd->AddOwnershipEdge(local_dump->guid(), global_dump->guid());
+    }
+  }
+  return true;
+}
+
+bool SharedMemoryTracker::IncrementMemoryUsage(
+    const SharedMemory& shared_memory) {
+  SharedMemoryHandleID id;
+  if (!GetIDFromSharedMemoryHandle(shared_memory.handle(), &id)) {
+    return false;
+  }
+  int bucket = id.file_id % kTrackerBucketNum;
+  base::AutoLock lock(buckets_[bucket].lock);
+  buckets_[bucket].usages[id] = shared_memory.mapped_size();
+  return true;
+}
+
+bool SharedMemoryTracker::DecrementMemoryUsage(
+    const SharedMemory& shared_memory) {
+  SharedMemoryHandleID id;
+  if (!GetIDFromSharedMemoryHandle(shared_memory.handle(), &id)) {
+    return false;
+  }
+  int bucket = id.file_id % kTrackerBucketNum;
+  base::AutoLock lock(buckets_[bucket].lock);
+  buckets_[bucket].usages.erase(id);
+  return true;
+}
+
+SharedMemoryTracker::SharedMemoryTracker() {
+  base::trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(
+      this, "SharedMemoryTracker", nullptr);
+}
+
+SharedMemoryTracker::~SharedMemoryTracker() {}
+
+SharedMemoryTracker::TrackerBucket::TrackerBucket() {}
+
+SharedMemoryTracker::TrackerBucket::~TrackerBucket() {}
+
+}  // namespace