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[ios/catalyst] fix memory leak with CollectionView

Open jonathanpeppers opened this issue 2 years ago • 3 comments

Fixes: https://github.com/dotnet/maui/issues/20710 Context: https://github.com/marco-skizza/MauiCollectionView

Testing the sample above, you can see a memory leak when setting up a CollectionView's DataTemplate in XAML, but it appears to work just fine with C#.

Using dotnet-gcdump with a Release build of the app, I see:

image

You can cause the C# version to leak, if you make the lambda an instance method:

  • https://github.com/jonathanpeppers/iOSMauiCollectionView/commit/3e5fb021fee3b512d8163c53224e17b76c3789c2

XAML just happens to use an instance method, no matter if XamlC is on/off.

I was able to reproduce this in CollectionViewTests.iOS.cs by making the CollectionView look like a "user control" and create an instance method.

There is a "cycle" that causes the problem here:

  • Microsoft.Maui.Controls.Handlers.Items.VerticalCell (note this is a UICollectionViewCell) ->
  • DataTemplate ->
  • Func<object> ->
  • PageXamlLeak (or PageCsOk w/ my change) ->
  • CollectionView ->
  • Microsoft.Maui.Controls.Handlers.Items.VerticalCell

The solution being to make TemplatedCell (which is a subclass of VerticalCell) hold only a WeakReference to the DataTemplate.

With this change in place, the test passes.

jonathanpeppers avatar Apr 15 '24 22:04 jonathanpeppers

CellsDoNotLeak test is failing on Catalyst (pass on iOS).

jsuarezruiz avatar Apr 16 '24 10:04 jsuarezruiz

CellsDoNotLeak test is failing on Catalyst (pass on iOS).

What is weird: the test passes when I run it by itself, but not when running the full suite.

jonathanpeppers avatar Apr 16 '24 14:04 jonathanpeppers

Retested the original sample app, the change seems to be working:

2024-04-16 14:39:15.575 MauiCollectionView[50559:5841573] Memory: 9498688
2024-04-16 14:39:21.874 MauiCollectionView[50559:5841573] Memory: 9690168
2024-04-16 14:39:22.810 MauiCollectionView[50559:5841573] Memory: 9868400
2024-04-16 14:39:23.485 MauiCollectionView[50559:5841584] ~PageXamlLeak() called
2024-04-16 14:39:23.487 MauiCollectionView[50559:5841573] Memory: 9870832
2024-04-16 14:39:24.193 MauiCollectionView[50559:5841573] Memory: 9897776
2024-04-16 14:39:24.872 MauiCollectionView[50559:5841584] ~PageXamlLeak() called
2024-04-16 14:39:24.875 MauiCollectionView[50559:5841573] Memory: 9879648
2024-04-16 14:39:25.576 MauiCollectionView[50559:5841573] Memory: 9901808
2024-04-16 14:39:26.257 MauiCollectionView[50559:5841584] ~PageCsOk() called
2024-04-16 14:39:26.260 MauiCollectionView[50559:5841573] Memory: 9883584
2024-04-16 14:39:26.943 MauiCollectionView[50559:5841573] Memory: 9908720

jonathanpeppers avatar Apr 16 '24 19:04 jonathanpeppers