Noticeable difference in RAM consumption and startup time between Qt 5.8 and Qt 5.7 QtQuick

Question

Official docs say that new Qt 5.8 release:

Quite a few things have happened in Qt QML and Qt Quick. The QML engine has gained support for caching binary representations of QML and JS files on disk, reducing startup time and memory consumption of the engine.

But it appears that neither startup time neither memory consumption has not been improved, furthermore it has become slower and more RAM is using.

I provided some tests. Created a new blank project, launched task manager and what I saw is:

Memory usage:

Qt 5.8 18.8 mb

Qt 5.7 14.2 mb

Startup time:

Difference about a second when I pushing a new item into a StackView via URL

So what did they improve?

Answer 1

Cashed code and data structures from .qml/.js files will be generated on the first start-up. The resulting .qmlc and .jsc cache files will be used for further start-ups, so you will not see any difference the first time your app starts.

My main project wich has more than 20k lines of code

It also depends on how your qml code is arranged and how big your qml files is, you need to minimize creating qml objects at start-up, divide your qml files into logical units and use Loader when possible.