[Development] Qt quick compiler impact on qmlbench.

Chris Adams chris.adams at qinetic.com.au
Wed Mar 3 04:10:50 CET 2021


On Wed, Mar 3, 2021 at 7:08 AM Robin Burchell <robin.burchell at crimson.no>

> On Tue, 2 Mar 2021, at 8:36 PM, Valery Volgutov wrote:
> > Could you please let me know why I have no any performance improvements
> > after quickcompiler apply?
> The QML compiler affects the performance of parsing and compiling the
> parsed source code. qmlbench is primarily testing the performance of object
> instantiation, binding evaluation, and the performance (or performance
> impacts) of various different properties. The code is only compiled once,
> but run repeatedly, which would also be more true of an application
> environment - you start your application once, not many times.
> I think there may be some other benchmarks that specifically cover startup
> time, but it's been a long time since I looked at it, so I don't really
> know where to point you off the top of my head.

The librarymetrics_performance benchmark in qtdeclarative has some
benchmarks for different phases (compilation, instantiation, layout and
positioning) but those were written before the qtquick compiler was a
thing, so I don't know how useful they'll be for this particular question.
At least it still builds and runs (my configure line was
~/src/qt6/qtbase/configure -developer-build -opensource -nomake examples
-platform linux-clang -confirm-license -xcb -xcb-xlib -release -- -D
QT_BUILD_BENCHMARKS=ON), and still produces results which seem at least
moderately sensible from what I can tell.
However, all of the data .qml files in that benchmark are very small /
specific.  For a more representative example of the sort of startup
performance improvement one might expect for an application, it may be
better to just try one of the larger QtQuick demo applications (e.g. Maroon
In Trouble) with compilation enabled and disabled, and compare the

Best regards,

> --
>   Robin Burchell
>   robin at crimson.no
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> Development at qt-project.org
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