[ios] avoid duplicating CALayer.Sublayer arrays
#21308
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In a customer's application, they saw in Xcode's Instruments:
4.4% Microsoft_Maui_Platform_StokeExtensions_UpdateBackgroundLayer_CoreAnimation_CALayer_CoreGraphics_CGRect
> 2.7% CoreAnimation_CALayer_get_Sublayers
Reviewing the code, there is a performance problem:
if (layer != null && layer.Sublayers != null)
{
foreach (var sublayer in layer.Sublayers)
{
//...
}
}
This accesses `CALayer.Sublayers` twice:
1. null check
2. `foreach`
When C# calls into Objective-C here, the returned array is marshaled
and copied to a C# array that can be consumed in managed code. We are
doing this work twice!
I audited all calls to `CALayer.Sublayers` and found that we can avoid
this in places that are called frequently.
This should improve the performance of all views on iOS or Catalyst.
However, I don't have access to the customer's application to test the
difference. We can have them try a nightly MAUI build after this is
merged.
jonathanpeppers
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legacy-area-perf
jonathanpeppers
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rmarinho
approved these changes
Mar 19, 2024
jonathanpeppers
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Apr 10, 2024
Context: #21580 Similar to: #21308 Recording this app in `dotnet-trace`, I saw: (0.81%) Microsoft.MacCatalyst!UIKit.UIView.get_Subviews() Where this time is spent in: * `Microsoft.Maui!Microsoft.Maui.Platform.WrapperView` Reviewing the code, it calls `this.Subviews` twice, which would marshal and create two arrays. It then calls `Subviews[0]`. Storing in a local instead will avoid creating the array twice: var subviews = Subviews; if (subviews.Length == 0) return; //... var child = subviews[0]; This improves things a small amount, but is probably worth it: (0.72%) Microsoft.MacCatalyst!UIKit.UIView.get_Subviews() I'll think about making an analyzer for this, but I didn't find any similar cases that appear in `dotnet-trace` at the moment. This doesn't fully solve #21580, but it's a small improvement.
rmarinho
pushed a commit
that referenced
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Apr 11, 2024
Context: #21580 Similar to: #21308 Recording this app in `dotnet-trace`, I saw: (0.81%) Microsoft.MacCatalyst!UIKit.UIView.get_Subviews() Where this time is spent in: * `Microsoft.Maui!Microsoft.Maui.Platform.WrapperView` Reviewing the code, it calls `this.Subviews` twice, which would marshal and create two arrays. It then calls `Subviews[0]`. Storing in a local instead will avoid creating the array twice: var subviews = Subviews; if (subviews.Length == 0) return; //... var child = subviews[0]; This improves things a small amount, but is probably worth it: (0.72%) Microsoft.MacCatalyst!UIKit.UIView.get_Subviews() I'll think about making an analyzer for this, but I didn't find any similar cases that appear in `dotnet-trace` at the moment. This doesn't fully solve #21580, but it's a small improvement.
Eilon
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Context: https://discord.com/channels/732297728826277939/732297808148824115/1219383992067821608
In a customer's application, they saw in Xcode's Instruments:
Reviewing the code, there is a performance problem:
This accesses
CALayer.Sublayerstwice:null check
foreachWhen C# calls into Objective-C here, the returned array is marshaled and copied to a C# array that can be consumed in managed code. We are doing this work twice!
I audited all calls to
CALayer.Sublayersand found that we can avoid this in places that are called frequently.This should improve the performance of all views on iOS or Catalyst. However, I don't have access to the customer's application to test the difference. We can have them try a nightly MAUI build after this is merged.