Unsolved QtQuick 2.0 TextEdit, TextArea, both are very-very slow on high-end PC

[vityafx4]

I have a very-very simple code:

import QtQuick 2.6
import QtQuick.Controls 1.5
import QtQuick.Dialogs 1.2

ApplicationWindow {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    menuBar: MenuBar {
        Menu {
            title: qsTr("File")
            MenuItem {
                text: qsTr("&Open")
                onTriggered: console.log("Open action triggered");
            }
            MenuItem {
                text: qsTr("Exit")
                onTriggered: Qt.quit();
            }
        }
    }

    TextArea {
        anchors.fill: parent
    }
}

If I paste a file of 6000 lines in the TextArea it is works very-very slow and laggy. However, the text scrolls quite fast, the interacting with it (selecting, writing, deleting) works very-very and very slow and freezy.
What can I do to increase performance? For example, QPlainTextEdit in c++ works much better.

Qt 5.6, Archlinux x64, i7 4790, 32gb ram.