Memory leak when scrolling a CollectionView with IsGrouped=true

[tranb3r]

Description

On android with net8-rc.1, I'm comparing the memory usage of a CollectionView with or without IsGrouped.
When scrolling a CollectionView with IsGrouped=true, the memory usage increases infinitely.
When scrolling a CollectionView with IsGrouped=false, the memory usage is stable.

Steps to Reproduce

1. Open repro project
2. On the first tab, tap on Add button, it will create a CollectionView with IsGrouped=false.
3. Scroll the CollectionView up and down. Observe memory usage with dotnet-gcdump. It is stable.
4. On the second tab, tap on Add button, it will create a CollectionView with IsGrouped=true.
5. Scroll the CollectionView up and down. Observe memory usage with dotnet-gcdump. It is slowly increasing.
6. Alternatively, open the attached gcdump files I've captured when scrolling the second tab. Between the first (memory-12.gcdump) and second (memory-19.gcdump), the size diff is +144,688 for object type List<Microsoft.Maui.Controls.Element>.

gcdump.zip

Link to public reproduction project repository

https://github.com/tranb3r/Issues/tree/main/MauiAppCollectionViewGroupingLeak

Version with bug

8.0.0-rc.1.9171

Is this a regression from previous behavior?

Not sure, did not test other versions

Last version that worked well

Unknown/Other

Affected platforms

Android

Affected platform versions

Android 34

Did you find any workaround?

No workaround

Relevant log output

No response

[ghost]

We've added this issue to our backlog, and we will work to address it as time and resources allow. If you have any additional information or questions about this issue, please leave a comment. For additional info about issue management, please read our Triage Process.

[tranb3r]

@jonathanpeppers @samhouts
I know you're busy with net8 GA preparations.
But I was hopping this issue could be investigated.
How can I help?

[mjsb212]

Profiling on 8.0.100-rc.2 shows same result in GC Dump

[jonathanpeppers]

Looking at @tranb3r's two dumps, I came to a similar conclusion that a List<Element> appears to just be growing and growing.

Let me investigate some more; thanks for filing this!

[jonathanpeppers]

My thoughts here, is the problem might be related to what I saw here:

• [android] CollectionView logical children grows with Header/Footer #17012

So, I tried something like this: main...jonathanpeppers:IsGroupedCollectionView

But the test passes, and I also don't think it fixes the sample app above.

I am going to be on vacation for a bit, so just writing this down for anyone else -- (or myself when I return 😄).

[tranb3r]

Any progress?

[mjsb212]

Also likely related to #18881 -- When I remove IsGrouped the scrolling is smooth with the GridItemsLayout & images. Anyone figure out why yet?

[jonathanpeppers]

@mjsb212 this one is specificly about CollectionView on Android. So if you are seeing an issue on another platform, file a new issue, thanks!

I'm putting this on the list of "scrolling performance" issues we're ramping up to work on in the next few months.

[mjsb212]

@tranb3r @jonathanpeppers -- Just to clarify: I am on Android and Release Build and after testing and profiling with dotnet trace & GC Dump, the issue I reported at #18881 seems to be related to this memory leak -- List<Element> appears to just be growing and growing when I have IsGrouped=true & that's why my large collection of images starts to lag as I scroll down & reach the end of the list. If I remove the grouping then all is fine, and scroll works well with the same exact size collection. Hope this one is addressed soon. After alot of profiling and testing I see .net 8.0 CollView has 100X better performance with most use cases, so thanks for all the work put in to address the performance issues -- looking forward to the 9.0. improvements.