【FuelPHP】Session::get()が遅い

前提・実現したいこと

fuelphpを使って開発をしています。
最近、バージョンを「1.8.0」から「1.8.1」に上げました。
ログイン処理はDBを使用し、認証成功ならセッションにユーザIDを格納しています。
その後の画面遷移ごとにセッションからユーザIDを確認しています。
Authパッケージは使用しています。

発生している問題・エラーメッセージ

ログインチェックする際に、セッションからユーザIDを取得するのですが、「1.8.1」にしてからすごい時間が掛かるようになりました。

該当のソースコード

ログイン成功時にセッションに値を格納。

public function complete_login($user_id) {
    Session::set('user_login', $user_id);　// ← ここは速い
    Session::instance()->rotate();
}

画面遷移ごとに行うログインチェック。

// ログインチェック
if (!Auth::check()) {
    Response::redirect('/');
    return;
}

Auth::check()から呼ばれるperform_check()が以下。

protected function perform_check() {
    $this->user = Session::get('user_login');　// ← ここに時間が掛かる
    return !empty($this->user);
}

試したこと

Session::get()しているところに固定値のユーザIDを入れたら前と同じくらいの処理時間になりました。

protected function perform_check() {
    $this->user = 'USER0001';　// ← 固定値にすると速い
    return !empty($this->user);
}

補足情報（FW/ツールのバージョンなど）

「1.8.0」から「1.8.1」にバージョンアップしてSessionクラスを見てみましたが、結構変わっていてどこが原因か特定できませんでした。

処理速度としましては10倍以上の差が出ています。
150msだったのが1,800msになったりとかです。

追加情報

// authのConfigです
<?php
return array(
    'driver' => 'Dbdriver',
    'verify_multiple_logins' => false,
    'salt' => 'dummy_salt',
    'iterations' => 10000,
);

config/config.php

<?php
/**
 * Fuel is a fast, lightweight, community driven PHP 5.4+ framework.
 *
 * @package    Fuel
 * @version    1.8.1
 * @author     Fuel Development Team
 * @license    MIT License
 * @copyright  2010 - 2018 Fuel Development Team
 * @link       http://fuelphp.com
 */

return array(
    // 'base_url'  => null,
    // 'url_suffix'  => '',
    'index_file' => '',
    'profiling'  => false,
    // 'cache_dir'       => APPPATH.'cache/',
    'caching'         => true,
    'cache_lifetime'  => 7200, // In Seconds
    // 'ob_callback'  => null,
    'language'           => 'ja', // Default language
    'language_fallback'  => 'en', // Fallback language when file isn't available for default language
    'locale'             => null,
    'encoding'  => 'UTF-8',
    'server_gmt_offset'  => 0,
    'default_timezone'   => 'Asia/Tokyo',
    'log_threshold'    => Fuel::L_ALL,
    // 'log_path'         => APPPATH.'logs/',
    'log_date_format'  => 'Y-m-d H:i:s',

    /**
     * Security settings
     */
    'security' => array(
        'csrf_autoload'            => false,
        // 'csrf_autoload_methods'    => array('post', 'put', 'delete'),
        // 'csrf_bad_request_on_fail' => false,
        // 'csrf_auto_token'          => false,
        'csrf_token_key'           => 'csrf_token',
        'csrf_expiration'          => 10000,

        /**
         * A salt to make sure the generated security tokens are not predictable
         */
        'token_salt' => 'dummy_token_salt',

        /**
         * Allow the Input class to use X headers when present
         *
         * Examples of these are HTTP_X_FORWARDED_FOR and HTTP_X_FORWARDED_PROTO, which
         * can be faked which could have security implications
         */
        // 'allow_x_headers'       => false,

        /**
         * This input filter can be any normal PHP function as well as 'xss_clean'
         *
         * WARNING: Using xss_clean will cause a performance hit.
         * How much is dependant on how much input data there is.
         */
        'uri_filter'       => array('htmlentities'),

        /**
         * This input filter can be any normal PHP function as well as 'xss_clean'
         *
         * WARNING: Using xss_clean will cause a performance hit.
         * How much is dependant on how much input data there is.
         */
        // 'input_filter'  => array(),

        /**
         * This output filter can be any normal PHP function as well as 'xss_clean'
         *
         * WARNING: Using xss_clean will cause a performance hit.
         * How much is dependant on how much input data there is.
         */
        'output_filter'  => array('Security::htmlentities'),

        /**
         * Encoding mechanism to use on htmlentities()
         */
        // 'htmlentities_flags' => ENT_QUOTES,

        /**
         * Whether to encode HTML entities as well
         */
        // 'htmlentities_double_encode' => false,

        /**
         * Whether to automatically filter view data
         */
        // 'auto_filter_output'  => true,

        /**
         * With output encoding switched on all objects passed will be converted to strings or
         * throw exceptions unless they are instances of the classes in this array.
         */
        'whitelisted_classes' => array(
            'Fuel\\Core\\Presenter',
            'Fuel\\Core\\Response',
            'Fuel\\Core\\View',
            'Fuel\\Core\\ViewModel',
            'Closure',
        ),
    ),

    /**
     * Cookie settings
     */
    // 'cookie' => array(
        // Number of seconds before the cookie expires
        // 'expiration'  => 0,
        // Restrict the path that the cookie is available to
        // 'path'        => '/',
        // Restrict the domain that the cookie is available to
        // 'domain'      => null,
        // Only transmit cookies over secure connections
        // 'secure'      => false,
        // Only transmit cookies over HTTP, disabling Javascript access
        // 'http_only'   => false,
    // ),

    /**
     * Validation settings
     */
    // 'validation' => array(
        /**
         * Whether to fallback to global when a value is not found in the input array.
         */
        // 'global_input_fallback' => true,
    // ),

    /**
     * Controller class prefix
     */
     // 'controller_prefix' => 'Controller_',

    /**
     * Routing settings
     */
    // 'routing' => array(
        /**
         * Whether URI routing is case sensitive or not
         */
        // 'case_sensitive' => true,

        /**
         *  Whether to strip the extension
         */
        // 'strip_extension' => true,
    // ),

    /**
     * To enable you to split up your application into modules which can be
     * routed by the first uri segment you have to define their basepaths
     * here. By default empty, but to use them you can add something
     * like this:
     *      array(APPPATH.'modules'.DS)
     *
     * Paths MUST end with a directory separator (the DS constant)!
     */
    'module_paths' => [
        APPPATH.'modules'.DS
    ],

    /**
     * To enable you to split up your additions to the framework, packages are
     * used. You can define the basepaths for your packages here. By default
     * empty, but to use them you can add something like this:
     *      array(APPPATH.'modules'.DS)
     *
     * Paths MUST end with a directory separator (the DS constant)!
     */
    'package_paths' => array(
        PKGPATH,
    ),

    /**************************************************************************/
    /* Always Load                                                            */
    /**************************************************************************/
    'always_load' => [

        /**
         * These packages are loaded on Fuel's startup.
         * You can specify them in the following manner:
         *
         * array('auth'); // This will assume the packages are in PKGPATH
         *
         * // Use this format to specify the path to the package explicitly
         * array(
         *     array('auth'    => PKGPATH.'auth/')
         * );
         */
        // 'packages'  => array(
        //     //'orm',
        // ),
        'packages'  => [
            'auth',
            'email',
        ],

        /**
         * These modules are always loaded on Fuel's startup. You can specify them
         * in the following manner:
         *
         * array('module_name');
         *
         * A path must be set in module_paths for this to work.
         */
        'modules' => [
            'AAA',
            'BBB',
        ],

        /**
         * Classes to autoload & initialize even when not used
         */
        // 'classes'  => array(),

        /**
         * Configs to autoload
         *
         * Examples: if you want to load 'session' config into a group 'session' you only have to
         * add 'session'. If you want to add it to another group (example: 'auth') you have to
         * add it like 'session' => 'auth'.
         * If you don't want the config in a group use null as groupname.
         */
        // 'config'  => array(),
        'config' => [
     ],

        /**
         * Language files to autoload
         *
         * Examples: if you want to load 'validation' lang into a group 'validation' you only have to
         * add 'validation'. If you want to add it to another group (example: 'forms') you have to
         * add it like 'validation' => 'forms'.
         * If you don't want the lang in a group use null as groupname.
         */
        // 'language'  => array(),
    ],

);

sessionのConfigはdefault（Core）のままで触ってはいません。

＜データベース＞
xamppの10.1.22-MariaDB、phpMyAdminのバージョンは4.8.5です。

お分かりになる方、どうぞご教授お願いします。