[Development] QT_XCB_NATIVE_PAINTING makes worse that without of it

Konstantin Tokarev annulen at yandex.ru
Fri Mar 22 17:23:00 CET 2019



22.03.2019, 19:08, "Allan Sandfeld Jensen" <kde at carewolf.com>:
> On Freitag, 22. März 2019 12:46:59 CET Denis Shienkov wrote:
>>  Hi guys.
>>
>>  I have iMX6 board with Qt 5.11.2 and Qt-widgets based application. I have
>>  compiled my Qt with an 'xcb_native_painting' option.
>>
>>  I was hoping that this would speed up my UI and reduce the load on the CPU,
>>  but I was greatly mistaken:
>>
>>  When the QT_XCB_NATIVE_PAINTING is not set, I got following top:
>>
>>  * Xorg: 3.6 %
>>  * app: 12.8 %
>>
>>  When the QT_XCB_NATIVE_PAINTING is *set*, I got following top:
>>
>>  * Xorg: 23 %
>>  * app: 4.5 %
>>
>>  What? QT_XCB_NATIVE_PAINTING makes it worse in 2x-times... WTF?
>
> Sounds like XCB isn't as well optimized as Qt is ;)
>
> Note though, that there are number of techniques to make the native painting
> faster, such as always using qpixmap so the images stays buffered on the
> server side. You might be able to massage your program to be faster with
> native painting, but the whole reason for switching to Qt side painting was
> that for the average application developer Qt side was faster.

Native painting should be most beneficial when using remote X11

-- 
Regards,
Konstantin



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