Method SSDHashKV

tensorflow/core/framework/embedding/ssd_hash_kv.h:141–189

class SSDHashKV : public KVInterface<K, V> {
 public:
  explicit SSDHashKV(const std::string& path,
                     FeatureDescriptor<V>* feat_desc)
  : feat_desc_(feat_desc) {
    path_ = io::JoinPath(
        path, "ssd_kv_" + std::to_string(Env::Default()->NowMicros()) + "_");
    hash_map_.max_load_factor(0.8);
    hash_map_.set_empty_key_and_value(EMPTY_KEY, nullptr);
    hash_map_.set_counternum(16);
    hash_map_.set_deleted_key(DELETED_KEY);
    evict_file_set_.max_load_factor(0.8);
    evict_file_set_.set_empty_key_and_value(EMPTY_KEY, -1);
    evict_file_set_.set_counternum(16);
    evict_file_set_.set_deleted_key(DELETED_KEY);

    is_async_compaction_ = true;
    TF_CHECK_OK(ReadBoolFromEnvVar("TF_SSDHASH_ASYNC_COMPACTION", true,
          &is_async_compaction_));

    std::string io_scheme = "mmap_and_madvise";
    TF_CHECK_OK(ReadStringFromEnvVar(
        "TF_SSDHASH_IO_SCHEME", "mmap_and_madvise", &io_scheme));
    emb_file_creator_ =  EmbFileCreatorFactory::Create(io_scheme);
    EmbFile* ef = emb_file_creator_->Create(path_, current_version_, BUFFER_SIZE);
    emb_files_.emplace_back(ef);

    if (!is_async_compaction_) {
      LOG(INFO) <<
        "Use Sync Compactor in SSDHashKV of Multi-tier Embedding Storage!";
      compaction_fn_ = [this](){Compaction();}; 
      check_buffer_fn_ = [this](){CheckBuffer();};
      save_kv_fn_ = [this](K key, const void* value_ptr,
          bool is_compaction=false) {
        SaveKV(key, value_ptr, is_compaction);
      };
    } else {
      LOG(INFO) <<
        "Use Async Compactor in SSDHashKV of Multi-tier Embedding Storage!";
      compaction_fn_ = [](){};
      check_buffer_fn_ = [this](){CheckBufferAsync();};
      save_kv_fn_ = [this](K key, const void* value_ptr,
          bool is_compaction=false) {
        SaveKVAsync(key, value_ptr, is_compaction);
      };
      compaction_thread_ = Env::Default()->StartThread(
          ThreadOptions(), "COMPACTION", [this]() {
            CompactionThread();
          });
    }
  }

  void Init() {
    val_len_ = feat_desc_->data_bytes();