QML Loader leaks memory
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Hi all,
I am developing application using Qt/QML. I have used QML Loader to load the qml file.when i load the file using loader it occupies memory but weird thing is when i load and unload the file in loader, every time i load file it takes few memory and memory is continuous increasing. can any one has solution ?
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Hi,
In general Loader should be unloading the previous item when a new one is loaded. It does use deleteLater, which means e.g. changing the source file in a loop will show increasing memory usage until the event loop runs.
What version of Qt are you using? How many different files are you loading (e.g. are you toggling between two different files, or loading x new files)? It's possible the component itself is being cached by the engine and not cleared, which means each time a new component was loaded for the first time it would show an increase that would persist.
Regards,
Michael -
Hi Michael,
I am using 35 different qml files and at a time only one or no one would be in loader. when i load the new qml file it increase the memory but strangly it is not releasing when i remove it from the loader.even after load-unload-load same file will also increase the memory but the different is, it occupies lesser memory than first time occupied. I am using qt 4.7.3 but i also checked with 4.7.4 and got same result.
if engine is not clearing the cache then how can i clear it?
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Hi,
Do you mean that on unload no memory is released, or or that only some of the memory is released? I would expect the latter to be the case, with the component cache growing each time a completely new qml file is loaded (and this growth should at worst be bounded by the number of unique qml files that need to be loaded).
You could try using QDeclarativeEngine::clearComponentCache() to see if that makes any difference in your case. There is also a manual gc() function you can call from JS to force garbage collection, though I wouldn't expect it to make a difference in this case.
Regards,
Michael -
Hi,
Yes exactly, Loader is not releasing memory when i specify source as null. but if now i assign new qml file (other than before assigned) it will allot memory from previously unfreed memory if possible. you can check by simply making Loader element which simply loads two different file which just contains lots of rectangles.
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Have you been able to resolve this? I'm running into this exact same thing.
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Our leak is very serious, on a fully loaded QML (images and stuff) it leaks about 1MB per load. Which is really bad considering we have about 128MB total memory on the Windows CE device we use. We have to reboot the Windows CE device way to often. (several times a day, TPHB is not really happy about that, nor am I).
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Hi altera,
I havent sort out this problem but rather to reduce start up delay leakage in my application i have loaded files only once and afterwards setting visible to true/false so finally i am not unloading file.
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Yes, that is what I tried as well but sadly due to the memory constraints that pushed us up right to the maximum. Which caused more out of memory errors.
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No I'm 100% sure on top of that I've recreated the leak using 2 empty QMLs
https://bugreports.qt-project.org/browse/QTBUG-26032?focusedCommentId=179280#comment-179280
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One thing that I did notice is that when I add
@m_View->engine()->clearComponentCache();@
The leak is 10 times worse!
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This is all rather scary. Happens for me, too - due to big JPGs/PNGs loaded, it adds +40MB per unload.
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4.7.4 + 4.8.2 I have not tested 5 since we require Windows CE support.
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In my case:
4.7.4, 4.8.1 - QtQuick 1.
Qt5.0.0 - QtQuick 2.
