chore: change thread_local to __thread when possible.

This should reduce the access cost to thread_local objects.

Signed-off-by: Roman Gershman <roman@dragonflydb.io>

src/server/blocking_controller_test.cc

@@ -1,4 +1,4 @@
-// Copyright 2022, DragonflyDB authors.  All rights reserved.
+// Copyright 2023, DragonflyDB authors.  All rights reserved.
 // See LICENSE for licensing terms.
 //
 
@@ -9,6 +9,7 @@
 #include "base/logging.h"
 #include "server/command_registry.h"
 #include "server/engine_shard_set.h"
+#include "server/server_state.h"
 #include "server/transaction.h"
 #include "util/uring/uring_pool.h"
 
@@ -38,6 +39,8 @@ constexpr size_t kNumThreads = 3;
 void BlockingControllerTest::SetUp() {
   pp_.reset(new uring::UringPool(16, kNumThreads));
   pp_->Run();
+  pp_->Await([](unsigned index, ProactorBase* p) { ServerState::Init(index); });
+
   shard_set = new EngineShardSet(pp_.get());
   shard_set->Init(kNumThreads, false);
 

src/server/dragonfly_test.cc

@@ -185,7 +185,7 @@ TEST_F(DflyEngineTest, EvalBug713b) {
   fibers_ext::Fiber fibers[kNumFibers];
 
   for (unsigned j = 0; j < kNumFibers; ++j) {
-    fibers[j] = pp_->at(1)->LaunchFiber([=] {
+    fibers[j] = pp_->at(1)->LaunchFiber([=, this] {
       for (unsigned i = 0; i < 50; ++i) {
         Run(StrCat("fb", j), {"eval", script, "3", kKeySid0, kKeySid1, kKeySid2});
       }

src/server/engine_shard_set.cc

@@ -76,7 +76,7 @@ ShardMemUsage ReadShardMemUsage(float wasted_ratio) {
 
 constexpr size_t kQueueLen = 64;
 
-thread_local EngineShard* EngineShard::shard_ = nullptr;
+__thread EngineShard* EngineShard::shard_ = nullptr;
 EngineShardSet* shard_set = nullptr;
 uint64_t TEST_current_time_ms = 0;
 

src/server/engine_shard_set.h

@@ -225,7 +225,7 @@ class EngineShard {
   Counter counter_[COUNTER_TOTAL];
   std::vector<Counter> ttl_survivor_sum_;  // we need it per db.
 
-  static thread_local EngineShard* shard_;
+  static __thread EngineShard* shard_;
 };
 
 class EngineShardSet {

src/server/main_service.cc

@@ -495,8 +495,7 @@ void Service::Init(util::AcceptServer* acceptor, util::ListenerInterface* main_i
                    const InitOpts& opts) {
   InitRedisTables();
 
-  pp_.AwaitFiberOnAll(
-      [&](uint32_t index, ProactorBase* pb) { ServerState::tlocal()->Init(index); });
+  pp_.Await([](uint32_t index, ProactorBase* pb) { ServerState::Init(index); });
 
   uint32_t shard_num = pp_.size() > 1 ? pp_.size() - 1 : pp_.size();
   shard_set->Init(shard_num, !opts.disable_time_update);
@@ -513,7 +512,7 @@ void Service::Shutdown() {
   // We mark that we are shutting down. After this incoming requests will be
   // rejected
   pp_.AwaitFiberOnAll([](ProactorBase* pb) {
-    ServerState::tlocal()->Shutdown();
+    ServerState::tlocal()->EnterLameDuck();
     facade::Connection::ShutdownThreadLocal();
   });
 
@@ -526,6 +525,7 @@ void Service::Shutdown() {
   request_latency_usec.Shutdown();
 
   shard_set->Shutdown();
+  pp_.Await([](ProactorBase* pb) { ServerState::tlocal()->Destroy(); });
 
   // wait for all the pending callbacks to stop.
   fibers_ext::SleepFor(10ms);

src/server/server_state.cc

@@ -18,7 +18,7 @@ ABSL_FLAG(uint32_t, interpreter_per_thread, 10, "Lua interpreters per thread");
 
 namespace dfly {
 
-thread_local ServerState ServerState::state_;
+__thread ServerState* ServerState::state_ = nullptr;
 
 void MonitorsRepo::Add(facade::Connection* connection) {
   VLOG(1) << "register connection "
@@ -60,12 +60,14 @@ ServerState::~ServerState() {
 }
 
 void ServerState::Init(uint32_t thread_index) {
-  gstate_ = GlobalState::ACTIVE;
-  thread_index_ = thread_index;
+  state_ = new ServerState();
+  state_->gstate_ = GlobalState::ACTIVE;
+  state_->thread_index_ = thread_index;
 }
 
-void ServerState::Shutdown() {
-  gstate_ = GlobalState::SHUTTING_DOWN;
+void ServerState::Destroy() {
+  delete state_;
+  state_ = nullptr;
 }
 
 Interpreter* ServerState::BorrowInterpreter() {

src/server/server_state.h

@@ -93,18 +93,22 @@ class ServerState {  // public struct - to allow initialization.
   };
 
   static ServerState* tlocal() {
-    return &state_;
+    return state_;
   }
 
   static facade::ConnectionStats* tl_connection_stats() {
-    return &state_.connection_stats;
+    return &state_->connection_stats;
   }
 
   ServerState();
   ~ServerState();
 
-  void Init(uint32_t thread_index);
-  void Shutdown();
+  static void Init(uint32_t thread_index);
+  static void Destroy();
+
+  void EnterLameDuck() {
+    state_->gstate_ = GlobalState::SHUTTING_DOWN;
+  }
 
   bool is_master = true;
   std::string remote_client_id_;  // for cluster support
@@ -206,7 +210,7 @@ class ServerState {  // public struct - to allow initialization.
   absl::flat_hash_map<std::string, base::Histogram> call_latency_histos_;
   uint32_t thread_index_ = 0;
 
-  static thread_local ServerState state_;
+  static __thread ServerState* state_;
 };
 
 }  // namespace dfly