def release_jruby_runtime_memory
    logger.info "Release JRuby runtime memory..."
    runtime = JRuby.runtime
    runtime.release_class_loader

    # Clear loaded features to allow sooner garbage collection of it.
    # JRuby runtime will not be garbage collected right away due to thread local soft references to JRuby ThreadContext objects.
    clear_loaded_features(runtime)

    # Clear boundMethods
    runtime.getBoundMethods.clear

    clear_concurrent_hash_map_fields(runtime)
    release_memory_of_large_objects(runtime)
  rescue => e
    logger.error "release_jruby_runtime_memory failed with #{e.class.name}: #{e.message}"
  end

  def clear_loaded_features(runtime)
    load_service = runtime.getLoadService
    load_service.getLoadedFeatures.clear

    f = load_service.java_class.declared_field("librarySearcher")
    f.accessible = true
    library_searcher = f.value(load_service)

    loaded_features_index_method = library_searcher.java_class.declared_method('getLoadedFeaturesIndex')
    loaded_features_index_method.accessible = true
    loaded_features_index = loaded_features_index_method.invoke(library_searcher)
    loaded_features_index.clear

    f = library_searcher.java_class.declared_field("loadedFeaturesIndex")
    f.accessible = true
    f.set_value(library_searcher, loaded_features_index.class.new)
  rescue => e
    logger.error "clear_loaded_features failed with #{e.class.name}: #{e.message}"
  end

  def clear_concurrent_hash_map_fields(runtime)
    %w(allModules constantNameInvalidators).each do |field_name|
      f = runtime.java_class.declared_field(field_name)
      f.accessible = true
      (value = f.value(runtime)).clear
      f.set_value(runtime, value.class.new)
    end
  rescue => e
    logger.error "clear_concurrent_hash_map_fields #{field_name} failed with #{e.class.name}: #{e.message}"
  end

  def release_memory_of_large_objects(runtime)
    {
      "symbolTable" => runtime.getSymbolTable.class.new(JRuby.runtime),
      "javaSupport" => runtime.loadJavaSupport
    }.each do |field_name, new_value|
      f = JRuby.runtime.java_class.declared_field(field_name)
      f.accessible = true
      f.set_value(runtime, new_value)
    end
  rescue => e
    logger.error "release_memory_of_large_objects #{field_name} failed with #{e.class.name}: #{e.message}"
  end