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 {
+
+const char* kSharedMemoryDumpName = "shared_memory";

[danakj, 2017/01/25 16:58:13]

static

[hajimehoshi, 2017/01/26 10:56:00]

Done.

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

[danakj, 2017/01/25 16:58:13]

I think you could just print the two components of the handle id here rather
than needing a temp string and the GetSMHandleIdString() function?

[ssid, 2017/01/25 23:03:06]

This function would be required later for the other components to add ownership
edges. But right now it is not required in this cl.

[hajimehoshi, 2017/01/26 10:56:00]

Right, a function to convert id into string would be needed for other platforms
since the id implementation would be different. This is not needed for now
anyway. Done.

+      auto guid = base::trace_event::MemoryAllocatorDumpGuid(dump_name);
+      base::trace_event::MemoryAllocatorDump* local_dump =

[danakj, 2017/01/25 16:58:13]

what deletes this?

[ssid, 2017/01/25 23:03:06]

This gets added to trace json file at
MemoryDumpManager::FinalizeDumpAndAddToTrace. This happens after collecting
memory dumps from all MemoryDumpProvider(s). After this it gets deleted.

+          pmd->CreateAllocatorDump(dump_name);
+      local_dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,

[ssid, 2017/01/25 23:03:06]

I think we need a TODO here saying this size reported is not resident size, but
is virtual size.

[hajimehoshi, 2017/01/26 10:56:00]

Done.

+                            base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+                            usage.second);
+      base::trace_event::MemoryAllocatorDump* global_dump =

[danakj, 2017/01/25 16:58:13]

what deletes this?

[ssid, 2017/01/25 23:03:06]

Same comment as above.

+          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());

[ssid, 2017/01/25 23:03:06]

Is there any way to identify if this is browser or renderer at this point? I
would like the memory attribution to be taken by the renderer / gpu process and
not the browser. The browser never actually uses the shared memory in most
cases.

If it's not possible lets solve this issue in later CLs.

[ssid, 2017/01/25 23:03:06]

We also need a TODO here saying this is currently double counting the shared
memory reported by gpu and discardable dump providers. Add ownership edges to
fix the double counting.

[hajimehoshi, 2017/01/26 10:56:00]

I'm not sure about this. I'll leave TODO here instead.

On 2017/01/25 23:03:06, ssid wrote:
Done.

+    }
+  }
+  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() {}

[danakj, 2017/01/25 16:58:13]

 = default for these 

[hajimehoshi, 2017/01/26 10:56:00]

Done.

+
+SharedMemoryTracker::TrackerBucket::TrackerBucket() {}
+
+SharedMemoryTracker::TrackerBucket::~TrackerBucket() {}
+
+}  // namespace