[tracing] Add memory statistics from level db clients to tracing.

extensions/browser/value_store/leveldb_value_store.cc

Index: extensions/browser/value_store/leveldb_value_store.cc
diff --git a/extensions/browser/value_store/leveldb_value_store.cc b/extensions/browser/value_store/leveldb_value_store.cc
index 39a1346df7d2c2ca41d92585254cf4401e397436..a0c35f4d2f89f73411053c1b76ce6c526ede4c56 100644
--- a/extensions/browser/value_store/leveldb_value_store.cc
+++ b/extensions/browser/value_store/leveldb_value_store.cc
@@ -8,9 +8,12 @@
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
 #include "base/logging.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/sys_string_conversions.h"
+#include "base/trace_event/memory_dump_manager.h"
+#include "base/trace_event/process_memory_dump.h"
 #include "content/public/browser/browser_thread.h"
 #include "extensions/browser/value_store/value_store_util.h"
 #include "third_party/leveldatabase/env_chromium.h"
@@ -59,10 +62,14 @@ LeveldbValueStore::LeveldbValueStore(const std::string& uma_client_name,
       "Extensions.Database.Open." + uma_client_name, 1,
       leveldb_env::LEVELDB_STATUS_MAX, leveldb_env::LEVELDB_STATUS_MAX + 1,
       base::Histogram::kUmaTargetedHistogramFlag);
+  base::trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(

[Primiano Tucci (use gerrit), 2015/10/15 08:59:53]

same here about threading and unregistration

[ssid, 2015/10/15 15:22:04]

Done.

+      this);
 }
 
 LeveldbValueStore::~LeveldbValueStore() {
   DCHECK_CURRENTLY_ON(BrowserThread::FILE);
+  base::trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(

[Primiano Tucci (use gerrit), 2015/10/15 08:59:53]

And I guess here you meant to UNregister, not re-register

[ssid, 2015/10/15 15:22:04]

Done.

+      this);
 
   // Delete the database from disk if it's empty (but only if we managed to
   // open it!). This is safe on destruction, assuming that we have exclusive
@@ -325,6 +332,29 @@ bool LeveldbValueStore::WriteToDbForTest(leveldb::WriteBatch* batch) {
   return !WriteToDb(batch).get();
 }
 
+bool LeveldbValueStore::OnMemoryDump(
+    const base::trace_event::MemoryDumpArgs& args,
+    base::trace_event::ProcessMemoryDump* pmd) {
+  if (!db_)

[Primiano Tucci (use gerrit), 2015/10/15 08:59:53]

you really need to think about threading here. What is the thread on which db_
lives, I think FILE thread? You can't ask to dump on an arbitrary thread and
then just access db_

[ssid, 2015/10/15 15:22:04]

Done.

+    return true;
+
+  std::string value;
+  uint64 size;
+  db_->GetProperty("leveldb.approximate-memory-usage", &value);
+  base::StringToUint64(value, &size);
+
+  base::trace_event::MemoryAllocatorDump* dump = pmd->CreateAllocatorDump(
+      base::StringPrintf("leveldb/value_store/%p", this));

[Primiano Tucci (use gerrit), 2015/10/15 08:59:53]

why not putting the uma_client_name or the basename(db_path) in the name?

[ssid, 2015/10/15 15:22:04]

Done.

+  dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
+                  base::trace_event::MemoryAllocatorDump::kUnitsBytes, size);
+
+  // Memory is allocated from system allocator (malloc).
+  pmd->AddSuballocation(dump->guid(),
+                        base::trace_event::MemoryDumpManager::GetInstance()
+                            ->system_allocator_pool_name());
+  return true;
+}
+
 scoped_ptr<ValueStore::Error> LeveldbValueStore::EnsureDbIsOpen() {
   DCHECK_CURRENTLY_ON(BrowserThread::FILE);