diff --git a/mace/core/file_storage.cc b/mace/core/file_storage.cc
index cf5f0099d77bf90d18151b6a31493f0d05aeee81..20e98c5431ff02dc561714f0208e1c157d5235d9 100644
--- a/mace/core/file_storage.cc
+++ b/mace/core/file_storage.cc
@@ -57,7 +57,7 @@ std::unique_ptr<KVStorage> FileStorageFactory::CreateStorage(
 }
 
 FileStorage::FileStorage(const std::string &file_path):
-    file_path_(file_path) {}
+    data_changed_(false), file_path_(file_path) {}
 
 int FileStorage::Load() {
   struct stat st;
@@ -151,6 +151,7 @@ bool FileStorage::Insert(const std::string &key,
                          const std::vector<unsigned char> &value) {
   utils::WriteLock lock(&data_mutex_);
   data_.emplace(key, value);
+  data_changed_ = true;
   return true;
 }
 
@@ -164,6 +165,7 @@ const std::vector<unsigned char> *FileStorage::Find(const std::string &key) {
 
 int FileStorage::Flush() {
   utils::WriteLock lock(&data_mutex_);
+  if (!data_changed_)  return 0;
   int fd = open(file_path_.c_str(), O_WRONLY | O_CREAT, 0600);
   if (fd < 0) {
     LOG(WARNING) << "open file " << file_path_
@@ -224,6 +226,7 @@ int FileStorage::Flush() {
                  << " failed, error code: " << errno;
     return -1;
   }
+  data_changed_ = false;
   return 0;
 }
 
diff --git a/mace/core/file_storage.h b/mace/core/file_storage.h
index 7ff12419f749540c5efc0cabdba9508b57546237..799719f3373d449b41a337dac754ea032ec80e4b 100644
--- a/mace/core/file_storage.h
+++ b/mace/core/file_storage.h
@@ -36,6 +36,7 @@ class FileStorage : public KVStorage {
   int Flush() override;
 
  private:
+  bool data_changed_;
   std::string file_path_;
   std::map<std::string, std::vector<unsigned char>> data_;
   utils::RWMutex data_mutex_;
diff --git a/mace/core/runtime/opencl/opencl_runtime.cc b/mace/core/runtime/opencl/opencl_runtime.cc
index 202a23cd16a29067531bb1c173a94435ba80e210..cf114f4d5b15c20ab2e522cbc18d7a49ea8606d3 100644
--- a/mace/core/runtime/opencl/opencl_runtime.cc
+++ b/mace/core/runtime/opencl/opencl_runtime.cc
@@ -348,8 +348,6 @@ OpenCLRuntime::OpenCLRuntime():
                                                       &err);
   MACE_CHECK_CL_SUCCESS(err);
 
-  this->program_map_changed_ = false;
-
   extern std::shared_ptr<KVStorageFactory> kStorageFactory;
   if (kStorageFactory != nullptr) {
     const std::string cl_compiled_file_name = "mace_cl_compiled_program.bin";
@@ -512,8 +510,6 @@ void OpenCLRuntime::BuildProgramFromSource(
 
     if (this->storage_ != nullptr) {
       this->storage_->Insert(built_program_key, content);
-      std::lock_guard<std::mutex> lock(program_map_changed_mutex_);
-      this->program_map_changed_ = true;
     }
 
     VLOG(3) << "Program from source: " << built_program_key;
@@ -567,13 +563,9 @@ cl::Kernel OpenCLRuntime::BuildKernel(
 
 void OpenCLRuntime::SaveBuiltCLProgram() {
   if (storage_ != nullptr) {
-    std::lock_guard<std::mutex> lock(program_map_changed_mutex_);
-    if (program_map_changed_) {
-      if (storage_->Flush() != 0) {
-        LOG(FATAL) << "Store OPENCL compiled kernel to file failed."
-            " Please Make sure the storage directory exist.";
-      }
-      program_map_changed_ = false;
+    if (storage_->Flush() != 0) {
+      LOG(FATAL) << "Store OPENCL compiled kernel to file failed."
+          " Please Make sure the storage directory exist.";
     }
   }
 }
diff --git a/mace/core/runtime/opencl/opencl_runtime.h b/mace/core/runtime/opencl/opencl_runtime.h
index 238ec734a65f4fad41537c28e381a0c84802aa8c..9588a3c6facaf78a0da1892632e53ef076dfbdb2 100644
--- a/mace/core/runtime/opencl/opencl_runtime.h
+++ b/mace/core/runtime/opencl/opencl_runtime.h
@@ -125,11 +125,9 @@ class OpenCLRuntime {
   std::shared_ptr<cl::CommandQueue> command_queue_;
   std::map<std::string, cl::Program> built_program_map_;
   std::mutex program_build_mutex_;
-  std::mutex program_map_changed_mutex_;
   std::string platform_info_;
   std::string opencl_version_;
   bool out_of_range_check_;
-  bool program_map_changed_;
   uint64_t device_gloabl_mem_cache_size_;
   uint32_t device_compute_units_;
   GPUType gpu_type_;
diff --git a/mace/utils/rwlock.h b/mace/utils/rwlock.h
index c3bd2a8845044174c725e33dbb04ff62444a3d74..851c7f71b2d556c100db8d3b2bde43e063492720 100644
--- a/mace/utils/rwlock.h
+++ b/mace/utils/rwlock.h
@@ -43,29 +43,22 @@ class RWMutex {
 class ReadLock {
  public:
   explicit ReadLock(RWMutex *rw_mutex): rw_mutex_(rw_mutex) {
-    if (rw_mutex_ == nullptr) {
-      return;
-    }
+    MACE_CHECK_NOTNULL(rw_mutex);
     std::unique_lock<std::mutex> lock(rw_mutex->mutex_);
-    rw_mutex->waiting_readers_++;
+    rw_mutex->waiting_readers_ += 1;
     rw_mutex->reader_cv_.wait(lock, [&]() -> bool {
       return rw_mutex->waiting_writers_ == 0 && rw_mutex->counter_ >= 0;
     });
-    rw_mutex->waiting_readers_--;
-    rw_mutex->counter_++;
+    rw_mutex->waiting_readers_ -= 1;
+    rw_mutex->counter_ += 1;
   }
   ~ReadLock() {
-    if (rw_mutex_ == nullptr) {
-      return;
-    }
     std::unique_lock<std::mutex> lock(rw_mutex_->mutex_);
     rw_mutex_->counter_ -= 1;
     if (rw_mutex_->waiting_writers_ > 0) {
       if (rw_mutex_->counter_ == 0) {
         rw_mutex_->writer_cv_.notify_one();
       }
-    } else {
-      rw_mutex_->reader_cv_.notify_all();
     }
   }
   ReadLock(const ReadLock &) = delete;
@@ -80,21 +73,16 @@ class ReadLock {
 class WriteLock {
  public:
   explicit WriteLock(RWMutex *rw_mutex): rw_mutex_(rw_mutex) {
-    if (rw_mutex_ == nullptr) {
-      return;
-    }
+    MACE_CHECK_NOTNULL(rw_mutex);
     std::unique_lock<std::mutex> lock(rw_mutex->mutex_);
-    rw_mutex->waiting_writers_++;
+    rw_mutex->waiting_writers_ += 1;
     rw_mutex->writer_cv_.wait(lock, [&]() -> bool {
       return rw_mutex->counter_ == 0;
     });
-    rw_mutex->waiting_writers_--;
-    rw_mutex->counter_--;
+    rw_mutex->waiting_writers_ -= 1;
+    rw_mutex->counter_ -= 1;
   }
   ~WriteLock() {
-    if (rw_mutex_ == nullptr) {
-      return;
-    }
     std::unique_lock<std::mutex> lock(rw_mutex_->mutex_);
     rw_mutex_->counter_ = 0;
     if (rw_mutex_->waiting_writers_ > 0) {