Jquerymobile 1.4+ popup too slow

Jquerymobile 1.4+ popup too slow

Hi there.

My environment are jquerymobile 1.4 and smartphone devices(both iphone5c and gallaxynote 3)
The main problem is that reaction time really bad what I desire.

As you know I can place a form inside my popup.
However when it opens, focus will be moved to textarea inside the popup,
Device reaction time is really bad both iPhone5S and gallaxyNote3.

It's terrible OS reaction  so far have been terrible.

How can I resolve this?

Here is my code below:
<a href="#popupLogin" data-rel="popup" data-position-to="window" class="ui-btn ui-corner-all ui-shadow ui-btn-inline ui-icon-check ui-btn-icon-left ui-btn-a" data-transition="pop">Sign in</a>
<div data-role="popup" id="popupLogin" data-theme="a" class="ui-corner-all">
    <form>
        <div style="padding:10px 20px;">
            <h3>Please sign in</h3>
            <label for="pop_description" class="ui-hidden-accessible">Username:</label>
            <textarea cols="40" rows="8" name="pop_description" id="pop_description"></textarea>
            <button type="submit" class="ui-btn ui-corner-all ui-shadow ui-btn-b ui-btn-icon-left ui-icon-check">Sign in</button>
        </div>
    </form>
</div>