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MMI Application very slow after migration from qt 5.6 to qt 5.9



  • Hello,
    I'm on issue for two days now, and have not found any clue for solving, so i'm asking you guys if you can tell me any tips for further investigation.
    By advance thanks a lot !

    Context :
    i were put on a MMI on Linux, developed and tested on qt 5.6 in qt creator. I tried it, and it was a classic MMI with buttons, actions and refresh.
    Two days ago, a colleague ask to our IT team to migrate to qt 5.9, which was apparently done without any problems.

    I rebuilt my application, and now any waiting time for refreshing window has been multiplicated by 5-10.
    By example, the display at startup needs now 15 seconds.

    I have tried to compile in debug, without debug. Nothings changes. I have compared ui files generated, in order to find something.

    I'm out of ideas for further tracks to explore. Anyone one of you can give me hint for investigation ?

    Thanks.

    Guillaume.


  • Qt Champions 2019

    @GuillaumeL You can try to profile your application using Valgrind (Callgrind) or https://perf.wiki.kernel.org/index.php/Main_Page to see where you app is spending time. You can use strace/ltrace to see what is going on.
    Also, did you check whether CPU usage and RAM consumption are high when your app is running.



  • @jsulm Sounds like good idea. I try this now.



  • @jsulm Ok, after using perf tool, it seems that my application used 90% overhead on two shared objetcs :

    • libz.so.1.2.7
    • libpng15.so.15.13.0

    So thanks a lot for your response which give me a new tool, and a new hope on solving this issue.
    Now i'm gonna work on link betwen my application, this two lib and qt.


  • Moderators

    @GuillaumeL
    If I may ask, why do you link agaisnt an external png-libary?
    Qt does come with it's own png support, IIRC.



  • @J.Hilk A really good question. As i have inherited of this project a few weeks ago, i didn't have check all installation and configuration. I guess this is the best way to have surprises.


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