base: Introduce SharedMemoryTracker for POSIX (but not macOS)

base/memory/shared_memory_tracker.cc

Index: base/memory/shared_memory_tracker.cc
diff --git a/base/memory/shared_memory_tracker.cc b/base/memory/shared_memory_tracker.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8613f595336ada19357c900cf0ab9bf4d243b7f4
--- /dev/null
+++ b/base/memory/shared_memory_tracker.cc
@@ -0,0 +1,92 @@
+// 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::Usage::Usage() = default;
+
+SharedMemoryTracker::Usage::Usage(const Usage& rhs) = default;
+
+SharedMemoryTracker::Usage::~Usage() = default;
+
+// static
+SharedMemoryTracker* SharedMemoryTracker::GetInstance() {
+  static SharedMemoryTracker* instance = new SharedMemoryTracker;
+  return instance;
+}
+
+void SharedMemoryTracker::IncrementMemoryUsage(
+    const SharedMemory& shared_memory) {
+  Usage usage;
+  // |shared_memory|'s unique ID must be generated here and it'd be too late at
+  // OnMemoryDump. An ID is generated with a SharedMemoryHandle, but the handle
+  // might already be closed at that time. Now IncrementMemoryUsage is called
+  // just after mmap and the handle must live then. See the discussion at
+  // crbug.com/604726#c30.
+  SharedMemory::UniqueId id;
+  if (!shared_memory.GetUniqueId(&id))
+    return;
+  usage.unique_id = id;
+  usage.size = shared_memory.mapped_size();
+  AutoLock hold(usages_lock_);
+  usages_[&shared_memory] = usage;
+}
+
+void SharedMemoryTracker::DecrementMemoryUsage(
+    const SharedMemory& shared_memory) {
+  AutoLock hold(usages_lock_);
+  usages_.erase(&shared_memory);
+}
+
+bool SharedMemoryTracker::OnMemoryDump(const trace_event::MemoryDumpArgs& args,
+                                       trace_event::ProcessMemoryDump* pmd) {
+  std::unordered_map<SharedMemory::UniqueId, size_t, SharedMemory::UniqueIdHash>
+      sizes;
+  {
+    AutoLock hold(usages_lock_);
+    for (const auto& usage : usages_)
+      sizes[usage.second.unique_id] += usage.second.size;
+  }
+  for (auto& size : sizes) {
+    const SharedMemory::UniqueId& id = size.first;
+    std::string dump_name = StringPrintf("%s/%lld.%lld", "shared_memory",
+                                         static_cast<long long>(id.first),
+                                         static_cast<long long>(id.second));
+    auto guid = trace_event::MemoryAllocatorDumpGuid(dump_name);
+    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(trace_event::MemoryAllocatorDump::kNameSize,
+                          trace_event::MemoryAllocatorDump::kUnitsBytes,
+                          size.second);
+    trace_event::MemoryAllocatorDump* global_dump =
+        pmd->CreateSharedGlobalAllocatorDump(guid);
+    global_dump->AddScalar(trace_event::MemoryAllocatorDump::kNameSize,
+                           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;
+}
+
+SharedMemoryTracker::SharedMemoryTracker() {
+  trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(
+      this, "SharedMemoryTracker", nullptr);
+}
+
+SharedMemoryTracker::~SharedMemoryTracker() = default;
+
+}  // namespace