WP-Admin edit.php & post.php slowdown after import of 10k users

Solved.

Had a custom author drop down function that causes a large query loop.

add_filter('wp_dropdown_users', 'cust_dropdown_users');
function cust_dropdown_users($output)
{
    $users = get_users();

    $output = "<select id=\"post_author_override\" name=\"post_author_override\" class=\"\">";

    //Leave the admin in the list
    $output .= "<option value=\"1\">Admin</option>";
    foreach ($users as $user) {
        $sel = ($GLOBALS['post']->post_author == $user->ID) ? "selected='selected'" : '';
        $output .= '<option value="' . $user->ID . '"' . $sel . '>' . $user->user_login . ' (' . $user->user_email . ')</option>';
    }
    $output .= "</select>";

    return $output;
}

Now trying to find a better way to select different authors (feel free to suggest!).