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  1. Qt
  2. QTBUG-63475

QML thread CPU usage is higher than previous Qt versions

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: P1: Critical
    • Resolution: Done
    • Affects Version/s: 5.9
    • Fix Version/s: 5.9
    • Component/s: Core: Threads
    • Labels:
    • Environment:
      VxWorks SR0500

      VxWorks GCC 4.8.1
    • Platform/s:
      VxWorks
    • Commits:
      9c6bbdaca97d58ce028c9395801b9d658953f51a

      Description

      On VxWorks it has been observed that the QML thread is consuming a very large amount of CPU time (between 45-50% per core) compared to previous versions of Qt (5.5.1) and to Qt 5.9 on other platforms. This leads to a big drop in rendering performance (7 fps vs 28 fps with 5.5.1). Suspending this thread seems to work around the issue without any adverse effects and gives ~33-38fps performance like with 5.5.1.

      It was noted that some paths changed in Qt, from:

      • :/scenegraph/shaders/smoothcolor.vert
      • :/scenegraph/shaders/smoothcolor.frag

      to:

      • :/qt-project.org/scenegraph/shaders/smoothcolor.vert
      • :/qt-project.org/scenegraph/shaders/smoothcolor.frag

      and this resulted in the same performance between 5.5.1 and 5.9 when tested on a Linux system. However there is a still an issue on VxWorks, giving around ~20-21 fps compared to ~33-38 fps with 5.5.1.

      With the thread suspended, frame rate is still down by 1-3%.

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            People

            Assignee:
            papetaja Pasi Petäjäjärvi
            Reporter:
            jakepetroules Jake Petroules (DO NOT ASSIGN ISSUES)
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              Dates

              Created:
              Updated:
              Resolved:

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