Only initialize the ThreadStatusData when necessary.

Summary:
Before this patch, any function call to ThreadStatusUtil might automatically initialize and register the thread status data.  However, if it is the user-thread making this call, the allocated thread-status-data will never be released as such threads are not managed by rocksdb.

In this patch, I remove the automatic-initialization part.  Thread-status data is only initialized and uninitialized in Env during the thread creation and destruction.

Test Plan:
db_test
thread_list_test
listener_test

Reviewers: igor, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D40017

util/env_posix.cc

@@ -1766,7 +1766,7 @@ class PosixEnv : public Env {
       ThreadPool* tp = meta->thread_pool_;
 #if ROCKSDB_USING_THREAD_STATUS
       // for thread-status
-      ThreadStatusUtil::SetThreadType(tp->env_,
+      ThreadStatusUtil::RegisterThread(tp->env_,
           (tp->GetThreadPriority() == Env::Priority::HIGH ?
               ThreadStatus::HIGH_PRIORITY :
               ThreadStatus::LOW_PRIORITY));

util/thread_status_updater.cc

@@ -15,6 +15,19 @@ namespace rocksdb {
 
 __thread ThreadStatusData* ThreadStatusUpdater::thread_status_data_ = nullptr;
 
+void ThreadStatusUpdater::RegisterThread(
+    ThreadStatus::ThreadType ttype, uint64_t thread_id) {
+  if (UNLIKELY(thread_status_data_ == nullptr)) {
+    thread_status_data_ = new ThreadStatusData();
+    thread_status_data_->thread_type = ttype;
+    thread_status_data_->thread_id = thread_id;
+    std::lock_guard<std::mutex> lck(thread_list_mutex_);
+    thread_data_set_.insert(thread_status_data_);
+  }
+
+  ClearThreadOperationProperties();
+}
+
 void ThreadStatusUpdater::UnregisterThread() {
   if (thread_status_data_ != nullptr) {
     std::lock_guard<std::mutex> lck(thread_list_mutex_);
@@ -24,18 +37,6 @@ void ThreadStatusUpdater::UnregisterThread() {
   }
 }
 
-void ThreadStatusUpdater::SetThreadID(uint64_t thread_id) {
-  auto* data = InitAndGet();
-  data->thread_id.store(thread_id, std::memory_order_relaxed);
-}
-
-void ThreadStatusUpdater::SetThreadType(
-    ThreadStatus::ThreadType ttype) {
-  auto* data = InitAndGet();
-  data->thread_type.store(ttype, std::memory_order_relaxed);
-  ClearThreadOperationProperties();
-}
-
 void ThreadStatusUpdater::ResetThreadStatus() {
   ClearThreadState();
   ClearThreadOperation();
@@ -44,7 +45,10 @@ void ThreadStatusUpdater::ResetThreadStatus() {
 
 void ThreadStatusUpdater::SetColumnFamilyInfoKey(
     const void* cf_key) {
-  auto* data = InitAndGet();
+  auto* data = Get();
+  if (data == nullptr) {
+    return;
+  }
   // set the tracking flag based on whether cf_key is non-null or not.
   // If enable_thread_tracking is set to false, the input cf_key
   // would be nullptr.
@@ -53,8 +57,8 @@ void ThreadStatusUpdater::SetColumnFamilyInfoKey(
 }
 
 const void* ThreadStatusUpdater::GetColumnFamilyInfoKey() {
-  auto* data = InitAndGet();
-  if (data->enable_tracking == false) {
+  auto* data = GetLocalThreadStatus();
+  if (data == nullptr) {
     return nullptr;
   }
   return data->cf_key.load(std::memory_order_relaxed);
@@ -62,9 +66,8 @@ const void* ThreadStatusUpdater::GetColumnFamilyInfoKey() {
 
 void ThreadStatusUpdater::SetThreadOperation(
     const ThreadStatus::OperationType type) {
-  auto* data = InitAndGet();
-  if (!data->enable_tracking) {
-    assert(data->cf_key.load(std::memory_order_relaxed) == nullptr);
+  auto* data = GetLocalThreadStatus();
+  if (data == nullptr) {
     return;
   }
   // NOTE: Our practice here is to set all the thread operation properties
@@ -82,9 +85,8 @@ void ThreadStatusUpdater::SetThreadOperation(
 
 void ThreadStatusUpdater::SetThreadOperationProperty(
     int i, uint64_t value) {
-  auto* data = InitAndGet();
-  if (!data->enable_tracking) {
-    assert(data->cf_key.load(std::memory_order_relaxed) == nullptr);
+  auto* data = GetLocalThreadStatus();
+  if (data == nullptr) {
     return;
   }
   data->op_properties[i].store(value, std::memory_order_relaxed);
@@ -92,27 +94,24 @@ void ThreadStatusUpdater::SetThreadOperationProperty(
 
 void ThreadStatusUpdater::IncreaseThreadOperationProperty(
     int i, uint64_t delta) {
-  auto* data = InitAndGet();
-  if (!data->enable_tracking) {
-    assert(data->cf_key.load(std::memory_order_relaxed) == nullptr);
+  auto* data = GetLocalThreadStatus();
+  if (data == nullptr) {
     return;
   }
   data->op_properties[i].fetch_add(delta, std::memory_order_relaxed);
 }
 
 void ThreadStatusUpdater::SetOperationStartTime(const uint64_t start_time) {
-  auto* data = InitAndGet();
-  if (!data->enable_tracking) {
-    assert(data->cf_key.load(std::memory_order_relaxed) == nullptr);
+  auto* data = GetLocalThreadStatus();
+  if (data == nullptr) {
     return;
   }
   data->op_start_time.store(start_time, std::memory_order_relaxed);
 }
 
 void ThreadStatusUpdater::ClearThreadOperation() {
-  auto* data = InitAndGet();
-  if (!data->enable_tracking) {
-    assert(data->cf_key.load(std::memory_order_relaxed) == nullptr);
+  auto* data = GetLocalThreadStatus();
+  if (data == nullptr) {
     return;
   }
   data->operation_stage.store(ThreadStatus::STAGE_UNKNOWN,
@@ -123,9 +122,8 @@ void ThreadStatusUpdater::ClearThreadOperation() {
 }
 
 void ThreadStatusUpdater::ClearThreadOperationProperties() {
-  auto* data = InitAndGet();
-  if (!data->enable_tracking) {
-    assert(data->cf_key.load(std::memory_order_relaxed) == nullptr);
+  auto* data = GetLocalThreadStatus();
+  if (data == nullptr) {
     return;
   }
   for (int i = 0; i < ThreadStatus::kNumOperationProperties; ++i) {
@@ -135,9 +133,8 @@ void ThreadStatusUpdater::ClearThreadOperationProperties() {
 
 ThreadStatus::OperationStage ThreadStatusUpdater::SetThreadOperationStage(
     ThreadStatus::OperationStage stage) {
-  auto* data = InitAndGet();
-  if (!data->enable_tracking) {
-    assert(data->cf_key.load(std::memory_order_relaxed) == nullptr);
+  auto* data = GetLocalThreadStatus();
+  if (data == nullptr) {
     return ThreadStatus::STAGE_UNKNOWN;
   }
   return data->operation_stage.exchange(
@@ -146,18 +143,16 @@ ThreadStatus::OperationStage ThreadStatusUpdater::SetThreadOperationStage(
 
 void ThreadStatusUpdater::SetThreadState(
     const ThreadStatus::StateType type) {
-  auto* data = InitAndGet();
-  if (!data->enable_tracking) {
-    assert(data->cf_key.load(std::memory_order_relaxed) == nullptr);
+  auto* data = GetLocalThreadStatus();
+  if (data == nullptr) {
     return;
   }
   data->state_type.store(type, std::memory_order_relaxed);
 }
 
 void ThreadStatusUpdater::ClearThreadState() {
-  auto* data = InitAndGet();
-  if (!data->enable_tracking) {
-    assert(data->cf_key.load(std::memory_order_relaxed) == nullptr);
+  auto* data = GetLocalThreadStatus();
+  if (data == nullptr) {
     return;
   }
   data->state_type.store(
@@ -222,11 +217,14 @@ Status ThreadStatusUpdater::GetThreadList(
   return Status::OK();
 }
 
-ThreadStatusData* ThreadStatusUpdater::InitAndGet() {
-  if (UNLIKELY(thread_status_data_ == nullptr)) {
-    thread_status_data_ = new ThreadStatusData();
-    std::lock_guard<std::mutex> lck(thread_list_mutex_);
-    thread_data_set_.insert(thread_status_data_);
+ThreadStatusData* ThreadStatusUpdater::GetLocalThreadStatus() {
+  if (thread_status_data_ == nullptr) {
+    return nullptr;
+  }
+  if (!thread_status_data_->enable_tracking) {
+    assert(thread_status_data_->cf_key.load(
+        std::memory_order_relaxed) == nullptr);
+    return nullptr;
   }
   return thread_status_data_;
 }
@@ -290,17 +288,14 @@ void ThreadStatusUpdater::EraseDatabaseInfo(const void* db_key) {
 
 #else
 
-void ThreadStatusUpdater::UnregisterThread() {
+void ThreadStatusUpdater::RegisterThread(
+    ThreadStatus::ThreadType ttype, uint64_t thread_id) {
 }
 
-void ThreadStatusUpdater::ResetThreadStatus() {
-}
-
-void ThreadStatusUpdater::SetThreadID(uint64_t thread_id) {
+void ThreadStatusUpdater::UnregisterThread() {
 }
 
-void ThreadStatusUpdater::SetThreadType(
-    ThreadStatus::ThreadType ttype) {
+void ThreadStatusUpdater::ResetThreadStatus() {
 }
 
 void ThreadStatusUpdater::SetColumnFamilyInfoKey(

util/thread_status_updater.h

@@ -118,8 +118,8 @@ class ThreadStatusUpdater {
   // Set the id of the current thread.
   void SetThreadID(uint64_t thread_id);
 
-  // Set the thread type of the current thread.
-  void SetThreadType(ThreadStatus::ThreadType ttype);
+  // Register the current thread for tracking.
+  void RegisterThread(ThreadStatus::ThreadType ttype, uint64_t thread_id);
 
   // Update the column-family info of the current thread by setting
   // its thread-local pointer of ThreadStateInfo to the correct entry.
@@ -198,9 +198,15 @@ class ThreadStatusUpdater {
   // The thread-local variable for storing thread status.
   static __thread ThreadStatusData* thread_status_data_;
 
-  // Obtain the pointer to the thread status data.  It also performs
-  // initialization when necessary.
-  ThreadStatusData* InitAndGet();
+  // Returns the pointer to the thread status data only when the
+  // thread status data is non-null and has enable_tracking == true.
+  ThreadStatusData* GetLocalThreadStatus();
+
+  // Directly returns the pointer to thread_status_data_ without
+  // checking whether enabling_tracking is true of not.
+  ThreadStatusData* Get() {
+    return thread_status_data_;
+  }
 
   // The mutex that protects cf_info_map and db_key_map.
   std::mutex thread_list_mutex_;

util/thread_status_util.cc

@@ -15,14 +15,14 @@ __thread ThreadStatusUpdater*
     ThreadStatusUtil::thread_updater_local_cache_ = nullptr;
 __thread bool ThreadStatusUtil::thread_updater_initialized_ = false;
 
-void ThreadStatusUtil::SetThreadType(
+void ThreadStatusUtil::RegisterThread(
     const Env* env, ThreadStatus::ThreadType thread_type) {
   if (!MaybeInitThreadLocalUpdater(env)) {
     return;
   }
   assert(thread_updater_local_cache_);
-  thread_updater_local_cache_->SetThreadID(env->GetThreadID());
-  thread_updater_local_cache_->SetThreadType(thread_type);
+  thread_updater_local_cache_->RegisterThread(
+      thread_type, env->GetThreadID());
 }
 
 void ThreadStatusUtil::UnregisterThread() {

util/thread_status_util.h

@@ -27,8 +27,8 @@ class ColumnFamilyData;
 // all function calls to ThreadStatusUtil will be no-op.
 class ThreadStatusUtil {
  public:
-  // Set the thread type of the current thread.
-  static void SetThreadType(
+  // Register the current thread for tracking.
+  static void RegisterThread(
       const Env* env, ThreadStatus::ThreadType thread_type);
 
   // Unregister the current thread.