.NET MAUI Shell app page navigation memory leaks

[duffh]

Description

In a .NET MAUI Shell app running on Windows it looks like pages are held in memory after navigating to and then away from the page. This results in an increase in memory over time as pages are opened and closed.

We noticed this issue as we have some particularly memory intensive pages that result in steep memory jumps as they are opened and closed.

Steps to Reproduce

Setup

1. Create new Maui app. File -> New Solution -> Maui App
2. Create two new MAUI ContentPages SecondaryPage and TertiaryPage
3. Add SecondaryPage to the Shell Flyout Items
4. Add a Button to the SecondaryPage with a clicked event await Navigation.PushAsync(new TertiaryPage());

Testing

1. Run the app targeting Windows
2. Navigate to the SecondaryPage via the Flyout
3. Navigate to the TertiaryPage via the Button on SecondaryPage
4. Click the back button
5. Take a snapshot of the memory usage
6. Navigate to the TertiaryPage via the Button on SecondaryPage
7. Click the back button
8. Take a snapshot of the memory usage
9. Repeat as many times as desired

Result: Looking at the memory usage snapshots the number of instances of TertiaryPage in memory increases with the number of times the page has been opened.

Expected: The page should no longer exist in memory after navigating away, the number of instances in memory should not increase as the page is repeatedly opened.

Link to public reproduction project repository

https://github.com/duffh/MauiMemoryLeakTestApp

Version with bug

8.0.0-preview.5.8529

Last version that worked well

Unknown/Other

Affected platforms

Windows, I was not able test on other platforms

Affected platform versions

Windows SDK 10.0.19041.0

Did you find any workaround?

No response

Relevant log output

No response

[jonathanpeppers]

If you disable XAML hot reload so this warning isn’t there:

Does it still happen?

You should also make sure GC.Collect() is called somewhere in the sample, just to avoid confusion there.

[duffh]

Seeing the same issue as before with hot reload disabled.

Added a button to manually call GC.Collect() and I'm seeing the same results as before.

[jonathanpeppers]

Did you push the change where you added GC.Collect()?

https://github.com/duffh/MauiMemoryLeakTestApp/commits/7e81ca10cd0b7a2c7d143a17bb7a0f8516c53b09

[duffh]

I have now pushed the changes, sorry for the delay.

[jonathanpeppers]

I think I'm seeing the memory leak here as well. I tested the existing memory leak tests we have with pages on Windows -- and they seem OK & pass. So, this seems like a new/unfixed problem.

My first guess, is it's related to setting up Shell:

private void Initialize()
{
	FlyoutItem flyoutItem = new FlyoutItem();
	flyoutItem.Title = "SecondaryPage";

	ShellContent shellContent = new ShellContent();
	shellContent.Content = new SecondaryPage();
	shellContent.Route = $"{nameof(SecondaryPage)}_test";

	flyoutItem.Items.Add(shellContent);

	this.Items.Add(flyoutItem);
}

Then somehow there is a leak if once you do await Navigation.PushAsync(new TertiaryPage()); from the SecondaryPage.

I don't see what is holding the TertiaryPage indefinitely (yet):

(some of these are ok, once you see it say "Cycle Detected" in this tree view)

I will keep investigating, thanks for filing this!

[duffh]

Great, thanks @jonathanpeppers !

[SarthakB26]

@duffh I think you should use Shell navigation i.e Shell.Current.GoToAsync("pagename");
Rather then Navigation.PushAsync(new TertiaryPage()); when using shell right or I am missing anything ?

https://learn.microsoft.com/en-us/dotnet/maui/fundamentals/shell/navigation

[jonathanpeppers]

I've taken the approach that it doesn't really matter if the sample isn't best practice -- MAUI shouldn't leak.

Navigation.PushAsync(new TertiaryPage()) is reasonable to expect it wouldn't leak.