[Interest] Slow graphics effect (due to _dl_resolve_runtime_avx)

[Ch'Gans]

On 26 November 2016 at 11:57, Thiago Macieira <thiago.macieira at intel.com> wrote:
> On sábado, 26 de novembro de 2016 11:37:39 PST Ch'Gans wrote:
>> I have run valgrind function profiler here, and it seems that my app
>> spend most of it's time in:
>> - QApplication::exec()/QGuiApplication::exec()
>> - _dl_runtime_resolv_avx/_dl_runtime_resolve_avx'2
>
> That's a useless result. Your tool is telling you not the proper time of each
> function, but the aggregate time of that function and everything it called.

Well, I thought that maybe the role of _dl_runtime_resolv_avx was to
actually only resolve the function, not execute it as well...

> It's like saying that your application spends most of its time in main. We
> knew that... Drill down and find out what's happening. Very likely, the effect
> you turned on is too slow for your CPU or GPU, or in combination with some
> other system-dependent use.

/proc/cpu tells me that the CPU supports AVX (no trace of AVX2). So
could it be a bug somewhere. basically the wrong implementation is
called, or my CPU is not good enough, well it's a modern AMD:  "AMD
FX(tm)-8320 Eight-Core Processor".

What I'm trying to find out, is that is it a Qt problem (relying on
AVX2 on a CPU that doesn't support it), or is it a KUbuntu problem, or
...

As well, is there a simple way to disable AVX2 within Qt?

I find it a bit crazy that Qt graphics performance are that bad on a
modern desktop computer using latest (or almost) AMD CPU.


Chris

>
> --
> Thiago Macieira - thiago.macieira (AT) intel.com
>   Software Architect - Intel Open Source Technology Center
>
> _______________________________________________
> Interest mailing list
> Interest at qt-project.org
> http://lists.qt-project.org/mailman/listinfo/interest