Reduce costs in ComponentDirectiveVisitor.VisitRazorDirective #11881
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Customer feedback ticket shows ~40% of CPU costs are in this method. Of the 32 seconds of CPU time in this method, 21 seconds are in it's calls to GetTypeNamespace and GetSpanWithoutGlobalPrefix. VisitRazorDirective is called many times (we'll call that number 'l'), depending on the number of directives in the page. Each call costs O(m x n) where m is the number of import statements in the page and n is the number of directives that aren't fully qualified. Evidently, for this customer on this page, this O(l * m * n) is too much. 1) GetTypeNamespace -- Reduced to O(n) calls by storing it's result in _nonFullyQualifiedComponents 2) GetSpanWithoutGlobalPrefix -- Reduced to O(l * m) by moving outside the innnermost loop Fixes: https://developercommunity.visualstudio.com/t/Razor-Development:-30-Second-CPU-Churn-A/10904811
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@dotnet/razor-compiler for reviews |
ToddGrun
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May 27, 2025
| internal sealed class ComponentDirectiveVisitor : DirectiveVisitor | ||
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| private readonly List<TagHelperDescriptor> _nonFullyQualifiedComponents = []; | ||
| private readonly List<(TagHelperDescriptor TagHelper, string TypeNamespace)> _nonFullyQualifiedComponents = []; |
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@chsienki -- can you take another look? I've changed it so that the innermost loop should be over a much smaller set of items.
… search for those with a matching namespace and add those taghelper descriptors.
333fred
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May 27, 2025
chsienki
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May 27, 2025
DustinCampbell
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May 27, 2025
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| namespace Microsoft.AspNetCore.Razor.Language; | ||
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| internal sealed class ReadOnlyMemoryOfCharComparer : IEqualityComparer<ReadOnlyMemory<char>> |
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Consider moving this helper into Microsoft.AspNetCore.Razor.Utilities.Shared.
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I originally had placed this under utilities, but hit a snag with it needing HashCodeCombiner which wasn't available there. Didn't want to start moving code around as part of this PR, so I just placed it in the most convenient location. Agreed that it should be more global though.
This was referenced May 29, 2025
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Customer feedback ticket shows ~40% of CPU costs are in this method. Of the 33 seconds of CPU time in this method, 21 seconds are in it's calls to GetTypeNamespace and GetSpanWithoutGlobalPrefix.
VisitRazorDirective is called many times (we'll call that number 'l'), depending on the number of directives in the page. Each call costs O(m x n) where m is the number of import statements in the page and n is the number of directives that aren't fully qualified. Evidently, for this customer on this page, this O(l * m * n) is too much.
Fixes: https://developercommunity.visualstudio.com/t/Razor-Development:-30-Second-CPU-Churn-A/10904811