[Interest] Dedicated GPU for Qt 5.15.3 QtQuick2

[Andreas Cord-Landwehr]

Hi, why this specific example has such peaks on the specific target device is 
super-hard to tell. Often, in my experience, on such embedded devices even 
small changes can make huge difference in performance (e.g. the used shaders, 
how memory & textures are managed between CPU and GPU). For understanding 
these peaks, the best approach is to do a trace of such a situation with e.g 
Perf (and best using Hotspot for looking at flamegraph plots for the traces).
If this does not help indicating the cause, lttng is the next best option, 
though IMO a little bit harder to use.

On a general suggestion about which devices to use, (please take in mind that 
my experience is from usually bigger setups where typically a Wayland 
compositor is involved):
- prefer GPUs with MESA drivers whenever possible, because it simplifies 
debugging, profiling and allows fixing of issues
- do an early PoC implementation on an eval board and check a performance 
baseline
- carefully look at board erratas (like the famously much too small designed 
AXIBUS memory connection on i.MX6 devices)

But most important, use a profiler, check PoC implementations on the board and 
figure our your key use cases. If you only draw simple rectangles, even SW 
rendering will suffice, if you want to do shader magic and render many 
polygones, then you have to look at a completely different set of devices.

Best regards,
Andreas

On Donnerstag, 1. Juli 2021 06:55:32 CEST Ramakanth Kesireddy wrote:
> The reason Iam asking this is because I see significant CPU load(80-90%
> spike for a split second or so) on the below target device with integrated
> gpu even with Qt Quick2 gallery example application while performing screen
> transitions
> 
> Any thoughts/recommendations are appreciated.
> 
> Best Regards,
> Ramakanth
> 
> On Wed, 30 Jun, 2021, 21:42 Ramakanth Kesireddy, <rama.kesi at gmail.com>
> 
> wrote:
> > The target device is on embedded Linux with TI AM3358 chipset single core
> > 
> > On Wed, 30 Jun, 2021, 21:25 Sérgio Martins, <sergio.martins at kdab.com>
> > 
> > wrote:
> >> On 2021-06-30 14:51, Ramakanth Kesireddy wrote:
> >> > Hi,
> >> > 
> >> > Am using Qt 5.15.3 with QtQuick2 and QtQuick2 controls running on
> >> > integrated GPU.
> >> > 
> >> > Is there any specific recommendation on hardware from Qt to have
> >> > dedicated
> >> > GPU though am aware that it needs to support OpenGL Es2 or higher and
> >> > 60fps?
> >> 
> >> Hi,
> >> 
> >> 
> >> QtQuick2 doesn't require a discrete graphics card and works well on most
> >> iGPUs I've seen in laptops/desktops.
> >> 
> >> 
> >> 
> >> Regards,
> >> --
> >> Sérgio Martins | sergio.martins at kdab.com | Senior Software Engineer
> >> Klarälvdalens Datakonsult AB, a KDAB Group company
> >> Tel: Sweden (HQ) +46-563-540090, USA +1-866-777-KDAB(5322)
> >> KDAB - The Qt, C++ and OpenGL Experts