[android] avoid OnLayout() for Label
#21291
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jonathanpeppers
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Applies to: dotnet#18505 Context: https://github.com/dotnet/maui/files/13251041/MauiCollectionView.zip I profiled the above sample with `dotnet-trace` with the following PRs applied locally: * dotnet#21229 * dotnet#21291 While scrolling, a lot of time is spent in `ResourceDictionary` lookups on an Android Pixel 5 device: 2.0% Microsoft.Maui.Controls!Microsoft.Maui.Controls.ResourceDictionary.TryGetValue(string,object&) Drilling in, I can see System.Linq's `Reverse()` method: 0.56% System.Linq!System.Linq.Enumerable.ReverseIterator<TSource_REF>.MoveNext() 0.14% System.Linq!System.Linq.Enumerable.Reverse(System.Collections.Generic.IEnumerable`1<TSource_REF>) 0.04% System.Linq!System.Linq.Enumerable.ReverseIterator<TSource_REF>..ctor(System.Collections.Generic.IEnumerable`1<TSource_REF>) 0.04% System.Linq!System.Linq.Enumerable.ReverseIterator<TSource_REF>.Dispose() `Reverse()` can be problematic as it can sometimes create a copy of the entire collection, in order to sort in reverse. We can juse use a reverse `for`-loop instead. The indexer, we can also avoid a double-lookup: if (dict.ContainsKey(index)) return dict[index]; And instead do: if (dict.TryGetValue(index, out var value)) return value; The MAUI project template seems to setup a few "merged" `ResourceDictionary` as it contains `Styles.xaml`, so this is why this code path is being hit. I wrote a BenchmarkDotNet benchmark, and it indicates the collection is being copied, as the 872 bytes of allocation occur: | Method | key | Mean | Error | StdDev | Gen0 | Allocated | |------------ |------------ |----------:|---------:|---------:|-------:|----------:| | TryGetValue | key0 | 11.45 ns | 0.026 ns | 0.023 ns | - | - | | Indexer | key0 | 24.72 ns | 0.133 ns | 0.118 ns | - | - | | TryGetValue | merged99,99 | 117.06 ns | 2.334 ns | 2.497 ns | 0.1042 | 872 B | | Indexer | merged99,99 | 145.60 ns | 2.737 ns | 2.286 ns | 0.1042 | 872 B | With these changes in place, I see less time spent inside: 0.91% Microsoft.Maui.Controls!Microsoft.Maui.Controls.ResourceDictionary.TryGetValue(string,object&) The benchmark no longer allocates either: | Method | key | Mean | Error | StdDev | Allocated | |------------ |------------ |----------:|----------:|----------:|----------:| | TryGetValue | key0 | 11.92 ns | 0.094 ns | 0.084 ns | - | | Indexer | merged99,99 | 23.12 ns | 0.418 ns | 0.391 ns | - | | Indexer | key0 | 24.20 ns | 0.485 ns | 0.453 ns | - | | TryGetValue | merged99,99 | 29.09 ns | 0.296 ns | 0.262 ns | - | This should improve the performance "parenting" of any MAUI view on all platforms -- as well as scrolling `CollectionView`.
Context: dotnet#18505 Context: https://github.com/dotnet/maui/files/13251041/MauiCollectionView.zip Context: dotnet#21229 (review) In profiling scrolling of an app with a `<CollectionView/>` and 12 `<Label/>`s, we see time spent in: 1.9% Microsoft.Maui!Microsoft.Maui.Platform.MauiTextView.OnLayout(bool,int,int,int,int) This is a callback from Java to C#, which has a performance cost. Reviewing the code, we would only need to make this callback *at all* if `Label.FormattedText` is not `null`. The bulk of all `Label`'s can avoid this call? To do this: * Write a new `PlatformAppCompatTextView.java` that override `onLayout()` * It only calls `onLayoutFormatted()` if a `isFormatted` `boolean` field is `true` * We can set `isFormatted` if a formatted string is such as: `isFormatted = !(text instanceof String)` With this change in place, the above `MauiTextView.OnLayout()` call is completely gone from `dotnet-trace` output. Scrolling the sample also "feels" a bit snappier. This should improve the performance of all non-formatted `Label`s on Android. This is the mininum amount of API changes possible -- which seems like what we should go for if we ship this change in .NET 8 servicing.
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| @Override | ||
| public void setText(CharSequence text, BufferType type) { | ||
| isFormatted = !(text instanceof String); | ||
| super.setText(text, type); | ||
| } |
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Note that calling TextView.Text = "foo" will call inside here:
The C# TextView.Text property is bound to setText(CharSequence).
jsuarezruiz
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Mar 27, 2024
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Applies to: #18505 Context: https://github.com/dotnet/maui/files/13251041/MauiCollectionView.zip I profiled the above sample with `dotnet-trace` with the following PRs applied locally: * #21229 * #21291 While scrolling, a lot of time is spent in `ResourceDictionary` lookups on an Android Pixel 5 device: 2.0% Microsoft.Maui.Controls!Microsoft.Maui.Controls.ResourceDictionary.TryGetValue(string,object&) Drilling in, I can see System.Linq's `Reverse()` method: 0.56% System.Linq!System.Linq.Enumerable.ReverseIterator<TSource_REF>.MoveNext() 0.14% System.Linq!System.Linq.Enumerable.Reverse(System.Collections.Generic.IEnumerable`1<TSource_REF>) 0.04% System.Linq!System.Linq.Enumerable.ReverseIterator<TSource_REF>..ctor(System.Collections.Generic.IEnumerable`1<TSource_REF>) 0.04% System.Linq!System.Linq.Enumerable.ReverseIterator<TSource_REF>.Dispose() `Reverse()` can be problematic as it can sometimes create a copy of the entire collection, in order to sort in reverse. We can juse use a reverse `for`-loop instead. The indexer, we can also avoid a double-lookup: if (dict.ContainsKey(index)) return dict[index]; And instead do: if (dict.TryGetValue(index, out var value)) return value; The MAUI project template seems to setup a few "merged" `ResourceDictionary` as it contains `Styles.xaml`, so this is why this code path is being hit. I wrote a BenchmarkDotNet benchmark, and it indicates the collection is being copied, as the 872 bytes of allocation occur: | Method | key | Mean | Error | StdDev | Gen0 | Allocated | |------------ |------------ |----------:|---------:|---------:|-------:|----------:| | TryGetValue | key0 | 11.45 ns | 0.026 ns | 0.023 ns | - | - | | Indexer | key0 | 24.72 ns | 0.133 ns | 0.118 ns | - | - | | TryGetValue | merged99,99 | 117.06 ns | 2.334 ns | 2.497 ns | 0.1042 | 872 B | | Indexer | merged99,99 | 145.60 ns | 2.737 ns | 2.286 ns | 0.1042 | 872 B | With these changes in place, I see less time spent inside: 0.91% Microsoft.Maui.Controls!Microsoft.Maui.Controls.ResourceDictionary.TryGetValue(string,object&) The benchmark no longer allocates either: | Method | key | Mean | Error | StdDev | Allocated | |------------ |------------ |----------:|----------:|----------:|----------:| | TryGetValue | key0 | 11.92 ns | 0.094 ns | 0.084 ns | - | | Indexer | merged99,99 | 23.12 ns | 0.418 ns | 0.391 ns | - | | Indexer | key0 | 24.20 ns | 0.485 ns | 0.453 ns | - | | TryGetValue | merged99,99 | 29.09 ns | 0.296 ns | 0.262 ns | - | This should improve the performance "parenting" of any MAUI view on all platforms -- as well as scrolling `CollectionView`.
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Context: #18505
Context: https://github.com/dotnet/maui/files/13251041/MauiCollectionView.zip
Context: #21229 (review)
In profiling scrolling of an app with a
<CollectionView/>and 12<Label/>s, we see time spent in:This is a callback from Java to C#, which has a performance cost.
Reviewing the code, we would only need to make this callback at all
if
Label.FormattedTextis notnull. The bulk of allLabel's canavoid this call?
To do this:
Write a new
PlatformAppCompatTextView.javathat overrideonLayout()It only calls
onLayoutFormatted()if aisFormattedbooleanfield is
trueWe can set
isFormattedif a formatted string is passed in, such as:isFormatted = !(text instanceof String)With this change in place, the above
MauiTextView.OnLayout()call iscompletely gone from
dotnet-traceoutput. Scrolling the sample also"feels" a bit snappier.
This should improve the performance of all non-formatted
Labels onAndroid.
This is the mininum amount of API changes possible -- which seems like
what we should go for if we ship this change in .NET 8 servicing.