Possible memory leak of gradient animation

SeeLook

Hi everyone,

I have such an animation:
Mem_leak.gif

But it changes duration every time and because of that memory usage grows and grows.
It eats RAM either under Qt 5.15.12 and Qt 6.6.1.
When I wrote this post it grew from 80 MB till 300 MB
Is it a bug to call or there is some misuse on my side?
Below is the code (sorry for long example but complexity of PathSvg matters :

import QtQuick 2.15
import QtQuick.Window 2.15
import QtQuick.Shapes 1.15

Window {
  id: pathWin
  width: 1366; height: 768
  color: "#bbb"

  property real grAnim: 0.0
  property int animDur: 2000

  NumberAnimation {
    id: goAnim
    running: true
    target: pathWin
    property: "grAnim"
    from: 0; to: 1
    duration: animDur
    onFinished: {
      animDur = 500 + Math.random() * 10000
      backAnim.start()
    }
  }
  NumberAnimation {
    id: backAnim
    target: pathWin
    property: "grAnim"
    from: 1; to: 0
    duration: animDur
    onFinished: {
      animDur = 500 + Math.random() * 10000
      goAnim.start()
    }
  }

  Shape {
    width: 269; height: 356
    antialiasing: true
    smooth: true
    rotation: 180; scale: 1.5

    ShapePath {
      strokeColor: "#777"
      strokeWidth: 2
      fillGradient: LinearGradient {
        x1: 134.5; y1: -400; x2: 134.5; y2: 400
        GradientStop { position: 0.0; color: "#005500" }
        GradientStop { position: grAnim * 0.9; color: "#005500" }
        GradientStop { position: 0.1 + grAnim * 0.9; color: "#AAA" }
      }
      PathSvg {
        //path: "" // quite complex path
      }
    }
  }
}

Entire code here.

mzimmers

@SeeLook this is just a wild guess, but...what happens if you remove the randomness from the durations? I'm wondering whether it's trying to cache some portion of your objects, but because the randomness makes each one different, it can't reuse them.

SeeLook

@mzimmers
When duration time is constant the memory usage is constant as well.

SeeLook

So far it seems not like a bug but intended caching.
I tried to remove/create this tree path every time the animation starts but no RAM is released:

property var tree: Qt.createComponent("TreeShape.qml").createObject(pathWin)

  NumberAnimation {
    id: goAnim
    running: true
    target: pathWin
    property: "grAnim"
    from: 0; to: 1
    duration: animDur
    onFinished: {
      animDur = 500 + Math.random() * 10000
      tree.destroy()
      tree = Qt.createComponent("TreeShape.qml").createObject(pathWin)
      backAnim.start()
    }
  }

So maybe it would be more proper to ask how to clean this cache?

mzimmers

@SeeLook from your description, this doesn't really seem like a true memory leak; it's more just a really memory-intensive application. I'm assuming that once it hits the 300 MB mark, it remains relatively steady?

SeeLook

@mzimmers
Unfortunately not.
The app is working on 1GB device and it crashes after 30 min of work exactly because of this kind of animation.
So I'm looking for solution.
If there is no simpler way, maybe I will try to implement that in C++ using QQuickPainedItem.

jsulm

@SeeLook Use a memory profiler (like Valgrind) to see what eats the memory.

SeeLook

@jsulm
Ok. Let's try. But please help me to interpret it:
memAtPeak.png

I can see that QQuickShapeGradientOpenGlCache takes 16 MB at peak but only 357 KiB at start.
Shall I share this massif tool dumped data?

jsulm

@SeeLook 16MB is not much, would be interesting to see it when a lot more RAM is used

SeeLook

@jsulm
Ok I will launch it again and share data.

SeeLook

@jsulm
After about 20 min.
massif_20min.png
.. and probably it would grow and grow

Here is full massif file

jsulm

@SeeLook Could be a bug in Qt. You can file a bug at https://bugreports.qt.io/secure/Dashboard.jspa

JKSH

The problem is that every unique value of grAnim causes a new texture to be generated and stored in the cache: https://bugreports.qt.io/browse/QTBUG-136553