[Development] QML instantiation performance

[Juha Vuolle]

Hey Chris,

Thanks heaps. I'll have a look and get back with any findings (may
take a day or two before I get to it).

cheers,
Juha

2014-11-27 3:51 GMT+02:00 Chris Adams <chris.adams at qinetic.com.au>:
> Hi Juha,
>
> For some more light on this issue, are you able to run the
> qtdeclarative/tests/benchmarks/qml/librarymetrics_performance benchmark on
> both 5.1 and 5.3 (you may have to backport to 5.1 as IIRC I made some
> changes to the way the components were instantiated for 5.2 before the
> benchmark was integrated, but I may be wrong about that.  It was originally
> written prior to Qt5.0 release so with some minor changes it will definitely
> work against 5.1).
>
> The benchmarks are quite granular, and should allow you to see precisely
> which part of the component instantiation is significantly slower.
>
> Kind regards,
> Chris Adams.
>
>
> www.qinetic.com.au - Qt And QML User Experience Specialists
>
> On Wed, Nov 26, 2014 at 6:08 PM, Juha Vuolle <juvuolle at gmail.com> wrote:
>>
>> Hello,
>>
>> apologies for cross-posting. I find this such a fundamental issue that I
>> feel
>> at least having the best possible understanding of it worth it (if any
>> exists, which is also
>> a valuable information in itself). I am happy to help if there is
>> anything I could check.
>>
>> thanks,
>> Juha
>>
>> ---
>>
>> Hello,
>>
>> I’m having trouble going from Qt 5.1 to 5.3 / 5.4 because of a
>> slowdown in QML (15..35% slower).
>> This primarily relates to component instantiation and seems quite
>> consistent across the platforms and
>> QPAs I’ve used recently.
>>
>> If you have any insights, thoughts or something I could check I would
>> highly appreciate them.
>>
>> I’ve tested on dual & quadcore imx6 (both EGLFS and XCB) embedded
>> platform as well as
>> few desktop Fedoras. I’ve tested with 5.1.1, 5.3.1 and the latest
>> 5.4.0. The slowdown varies
>> but is fairly consistently between 15..35 %. Instantiation CPU loads
>> do not seem to be particularly high (< 70%).
>>
>> Running QML profiler seems to make results less predictable. So I made
>> a very simple application startup timer
>> that checks main() -> QQuickWindow::beforeSynchronizing() ->
>> beforeRendering() -> afterRendering() -> frameSwapped().
>> Please find my "highly scientific" measurements below. I slowed down
>> the CPU to make things more clear on the desktop I’m writing
>> this email from. This behaviour is not specific to only application
>> startup but later runtime instantiations seem also slower.
>>
>> I am grateful for any thoughts or things I could check.
>>
>> Thanks,
>> Juha
>>
>> Qt 5.1.1 low CPU qtquickcontrols gallery example startup:
>> 1. onBeforeSynchronizing() for the FIRST time, time it took from main():
>> 950
>> 2. onBeforeRendering() time it took from beforeSynchronizing: 3
>> 3. onAfterRendering() time it took from beforeRendering: 1572
>> 4. onFrameSwapped() time it took from afterRendering: 5
>> = 2530 ms for first frame swapped.
>>
>> Qt 5.3.1 low CPU qtquickcontrols gallery example startup:
>> 1. onBeforeSynchronizing() for the FIRST time, time it took from main():
>> 1843
>> 2. onBeforeRendering() time it took from beforeSynchronizing: 364
>> 3. onAfterRendering() time it took from beforeRendering: 1039
>> 4. onFrameSwapped() time it took from afterRendering: 83
>> = 3329 ms for first frame swapped.
>>
>> Qt 5.1.1 low CPU my application startup:
>> 1. onBeforeSynchronizing() for the FIRST time, time it took from main():
>> 809
>> 2. onBeforeRendering() time it took from beforeSynchronizing: 3
>> 3. onAfterRendering() time it took from beforeRendering: 1373
>> 4. onFrameSwapped() time it took from afterRendering: 88
>> = 2273 ms for the first frame swapped
>>
>> Qt 5.3.1 low CPU my application startup:
>> 1. onBeforeSynchronizing() for the FIRST time, time it took from main():
>> 1341
>> 2. onBeforeRendering() time it took from beforeSynchronizing: 4
>> 3. onAfterRendering() time it took from beforeRendering: 2184
>> 4. onFrameSwapped() time it took from afterRendering: 10
>> = 3539 ms for the first frame swapped
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