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Reduce allocations in Razor's DirectiveVisitor #10537

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merged 2 commits into from
Jun 27, 2024
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Reduce allocations in Razor's DirectiveVisitor #10537

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e8f03f4
Reduce allocations in Razor's DirectiveVisitor
ToddGrun Jun 25, 2024
782d7a6
Switch from ArrayBuilderPool to ListPool
ToddGrun Jun 25, 2024
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42 changes: 27 additions & 15 deletions ...ft.CodeAnalysis.Razor.Compiler/src/Language/DefaultRazorTagHelperContextDiscoveryPhase.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -69,6 +69,8 @@ protected override void ExecuteCore(RazorCodeDocument codeDocument)
var context = TagHelperDocumentContext.Create(tagHelperPrefix, matches.ToImmutableArray());
codeDocument.SetTagHelperContext(context);
codeDocument.SetPreTagHelperSyntaxTree(syntaxTree);

visitor.Dispose();
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Consider using (visitor) { on line 55-ish, and ending it here, so its clearer to everyone that its being disposed, and so that there is a try..finally in place

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I can change to that, I didn't go that route initially as it didn't fall directly into the using pattern and it's really not a big deal if the disposal doesn't end up happening.

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and it's really not a big deal if the disposal doesn't end up happening

Is it not? I would have thought that would mean the pool allocates lots of new builders, defeating the purpose of the PR.

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Let me rephrase, it's not a big deal if it's an exceptional case where this occurs, not if it's the normal code path (which would probably indicate bigger problems than avoiding these allocations)

}

private static bool MatchesDirective(TagHelperDescriptor descriptor, string typePattern, string assemblyName)
Expand Down Expand Up @@ -106,32 +108,34 @@ private static ReadOnlySpan<char> RemoveGlobalPrefix(in ReadOnlySpan<char> span)
return span;
}

internal abstract class DirectiveVisitor(HashSet<TagHelperDescriptor> matches) : SyntaxWalker
internal abstract class DirectiveVisitor(HashSet<TagHelperDescriptor> matches) : SyntaxWalker, IDisposable
{
protected readonly HashSet<TagHelperDescriptor> Matches = matches;

public abstract string TagHelperPrefix { get; }

public abstract void Visit(RazorSyntaxTree tree);

public abstract void Dispose();
}

internal sealed class TagHelperDirectiveVisitor : DirectiveVisitor
{
private readonly List<TagHelperDescriptor> _tagHelpers;
private readonly PooledObject<ImmutableArray<TagHelperDescriptor>.Builder> _tagHelpers;
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Random thought: Is ImmutableArray the best choice here? Since this builder is never realized, a pooled list might be just as suitable, but a bit simpler, especially if an initial capacity can be set?

Looks like ImmutableArray<>.Builder just resizes an array anyway, so I can't imagine List would be any worse, but I don't really have any knowledge here.

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Or even just a PooledArrayBuilder<T>?

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I tried PooledArrayBuilder initially, and it didn't seem to work because I was trying to store that into a field, and that type is defined as a NonCopyable struct.

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I didn't go with PooledList as I talked to Andrew and we weren't sure of it's benefit. It's a struct, but not marked as non-copyable, so it could be used, but it doesn't seem to be used a lot throughout the codebase. I'm flexible, and can go with that (or whatever else works) if you'd prefer.

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@davidwengier davidwengier Jun 25, 2024 •
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Yeah, PooledList can't be used, but we also have ListPool which can. Isn't coding fun?!

(sorry, my bad when i said "pooled list" and wasn't specific. I knew we had one that was a ref struct, but couldn't remember which)

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Yeah, this feels cleaner. Thanks for the suggestions!

private string _tagHelperPrefix;

public TagHelperDirectiveVisitor(IReadOnlyList<TagHelperDescriptor> tagHelpers, HashSet<TagHelperDescriptor> matches)
: base(matches)
{
// We don't want to consider components in a view document.
_tagHelpers = new();
_tagHelpers = ArrayBuilderPool<TagHelperDescriptor>.GetPooledObject();

for (var i = 0; i < tagHelpers.Count; i++)
{
var tagHelper = tagHelpers[i];
if (!tagHelper.IsAnyComponentDocumentTagHelper())
{
_tagHelpers.Add(tagHelper);
_tagHelpers.Object.Add(tagHelper);
}
}
}
Expand Down Expand Up @@ -165,13 +169,13 @@ public override void VisitRazorDirective(RazorDirectiveSyntax node)
continue;
}

if (!AssemblyContainsTagHelpers(addTagHelper.AssemblyName, _tagHelpers))
if (!AssemblyContainsTagHelpers(addTagHelper.AssemblyName, _tagHelpers.Object))
{
// No tag helpers in the assembly.
continue;
}

foreach (var tagHelper in _tagHelpers)
foreach (var tagHelper in _tagHelpers.Object)
{
if (MatchesDirective(tagHelper, addTagHelper.TypePattern, addTagHelper.AssemblyName))
{
Expand All @@ -189,13 +193,13 @@ public override void VisitRazorDirective(RazorDirectiveSyntax node)
}


if (!AssemblyContainsTagHelpers(removeTagHelper.AssemblyName, _tagHelpers))
if (!AssemblyContainsTagHelpers(removeTagHelper.AssemblyName, _tagHelpers.Object))
{
// No tag helpers in the assembly.
continue;
}

foreach (var tagHelper in _tagHelpers)
foreach (var tagHelper in _tagHelpers.Object)
{
if (MatchesDirective(tagHelper, removeTagHelper.TypePattern, removeTagHelper.AssemblyName))
{
Expand All @@ -217,7 +221,7 @@ public override void VisitRazorDirective(RazorDirectiveSyntax node)
}
}

private static bool AssemblyContainsTagHelpers(string assemblyName, List<TagHelperDescriptor> tagHelpers)
private static bool AssemblyContainsTagHelpers(string assemblyName, ImmutableArray<TagHelperDescriptor>.Builder tagHelpers)
{
foreach (var tagHelper in tagHelpers)
{
Expand All @@ -229,11 +233,16 @@ private static bool AssemblyContainsTagHelpers(string assemblyName, List<TagHelp

return false;
}

public override void Dispose()
{
_tagHelpers.Dispose();
}
}

internal sealed class ComponentDirectiveVisitor : DirectiveVisitor
{
private readonly ImmutableArray<TagHelperDescriptor> _notFullyQualifiedComponents;
private readonly PooledObject<ImmutableArray<TagHelperDescriptor>.Builder> _notFullyQualifiedComponents;
private readonly string _filePath;
private RazorSourceDocument _source;

Expand All @@ -242,7 +251,7 @@ public ComponentDirectiveVisitor(string filePath, IReadOnlyList<TagHelperDescrip
{
_filePath = filePath;

using var builder = new PooledArrayBuilder<TagHelperDescriptor>(capacity: tagHelpers.Count);
_notFullyQualifiedComponents = ArrayBuilderPool<TagHelperDescriptor>.GetPooledObject();

for (var i = 0; i < tagHelpers.Count; i++)
{
Expand All @@ -260,7 +269,7 @@ public ComponentDirectiveVisitor(string filePath, IReadOnlyList<TagHelperDescrip
continue;
}

builder.Add(tagHelper);
_notFullyQualifiedComponents.Object.Add(tagHelper);

if (currentNamespace is null)
{
Expand All @@ -282,8 +291,6 @@ public ComponentDirectiveVisitor(string filePath, IReadOnlyList<TagHelperDescrip
Matches.Add(tagHelper);
}
}

_notFullyQualifiedComponents = builder.DrainToImmutable();
}

// There is no support for tag helper prefix in component documents.
Expand Down Expand Up @@ -343,7 +350,7 @@ public override void VisitRazorDirective(RazorDirectiveSyntax node)
continue;
}

foreach (var tagHelper in _notFullyQualifiedComponents)
foreach (var tagHelper in _notFullyQualifiedComponents.Object)
{
Debug.Assert(!tagHelper.IsComponentFullyQualifiedNameMatch, "We've already processed these.");

Expand Down Expand Up @@ -427,5 +434,10 @@ internal static bool IsTagHelperFromMangledClass(TagHelperDescriptor tagHelper)
{
return ComponentMetadata.IsMangledClass(tagHelper.GetTypeNameIdentifier());
}

public override void Dispose()
{
_notFullyQualifiedComponents.Dispose();
}
}
}
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