How resize the Action Bar Menu Text Size in Android

I am developing the android application. have one doubt regarding reduce the text size for action bar menu item. this my code.

 <resources xmlns:android="http://ift.tt/nIICcg">

    <style name="AppTheme" parent="@style/Theme.AppCompat.Light">
        <item name="actionBarStyle">@style/MyStyledActionBar</item>
        <item name="android:typeface">serif</item>
        <item name="android:textSize">20sp</item>
    </style>

    <style name="MyStyledActionBar" parent="@style/Widget.AppCompat.Light.ActionBar">
        <item name="background">@drawable/bg_action_bar</item>
        <item name="height">50dp</item>
        <item name="titleTextStyle">@style/MyActionBarTitleText</item>
        <item name="actionMenuTextAppearance">@style/MyActionBarMenuText</item>
        <item name="actionMenuTextColor">@style/MyActionBarMenuText</item>
    </style>

    <style name="MyActionBarTitleText" parent="@style/TextAppearance.AppCompat.Widget.ActionBar.Title">
        <item name="android:textColor">@color/actionBarText</item>
    </style>

    <style name="MyActionBarMenuText" parent="@style/TextAppearance.AppCompat.Widget.ActionBar.Menu">
        <item name="android:textColor">@color/actionBarText</item>
    </style>

</resources>