base: Introduce SharedMemoryTracker for POSIX (but not macOS)

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 {
+
+SharedMemoryTracker* SharedMemoryTracker::GetInstance() {
+  return base::Singleton<SharedMemoryTracker, base::LeakySingletonTraits<

[danakj, 2017/02/24 15:30:28]

I *think* the result of the "[chromium-dev] Making LazyInstance Leaky by
default" thread was that LazyInstance should be preferred over Singleton?

[hajimehoshi, 2017/02/27 07:51:54]

Done.

+                                                  SharedMemoryTracker>>::get();
+}
+
+bool SharedMemoryTracker::OnMemoryDump(
+    const base::trace_event::MemoryDumpArgs& args,
+    base::trace_event::ProcessMemoryDump* pmd) {
+  std::unordered_map<SharedMemory::Id, size_t, SharedMemory::IdHash> sizes;
+  {
+    base::AutoLock hold(lock_);
+    for (const auto& usage : usages_) {
+      SharedMemory::Id id;
+      usage.first->GetUniqueId(&id);

[danakj, 2017/02/24 15:30:28]

What if this returns false?

[hajimehoshi, 2017/02/27 07:51:54]

The sizes should not be recorded when it returns false. ID is not available in
some cases, and I'll care this later. Added TODO. Done.

+      sizes[id] += usage.second;
+    }
+  }
+  for (auto& size : sizes) {
+    const SharedMemory::Id& id = size.first;
+    std::string dump_name = base::StringPrintf(
+        "%s/%lld.%lld", "shared_memory", static_cast<long long>(id.first),
+        static_cast<long long>(id.second));
+    auto guid = base::trace_event::MemoryAllocatorDumpGuid(dump_name);
+    base::trace_event::MemoryAllocatorDump* local_dump =
+        pmd->CreateAllocatorDump(dump_name);
+    // TODO(hajimehoshi): The size is not resident size but virtual size so far.
+    // Fix this to record resident size.
+    local_dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
+                          base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+                          size.second);
+    base::trace_event::MemoryAllocatorDump* global_dump =
+        pmd->CreateSharedGlobalAllocatorDump(guid);
+    global_dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
+                           base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+                           size.second);
+    // TOOD(hajimehoshi): Detect which the shared memory comes from browser,
+    // renderer or GPU process.
+    // TODO(hajimehoshi): Shared memory reported by GPU and discardable is
+    // currently double-counted. Add ownership edges to avoid this.
+    pmd->AddOwnershipEdge(local_dump->guid(), global_dump->guid());
+  }
+  return true;
+}
+
+void SharedMemoryTracker::IncrementMemoryUsage(
+    const SharedMemory& shared_memory) {
+  base::AutoLock hold(lock_);
+  usages_[&shared_memory] = shared_memory.mapped_size();
+}
+
+void SharedMemoryTracker::DecrementMemoryUsage(
+    const SharedMemory& shared_memory) {
+  base::AutoLock hold(lock_);
+  usages_.erase(&shared_memory);
+}
+
+SharedMemoryTracker::SharedMemoryTracker() {
+  base::trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(
+      this, "SharedMemoryTracker", nullptr);
+}
+
+SharedMemoryTracker::~SharedMemoryTracker() = default;
+
+}  // namespace