Using Segmented collections to avoid LOH allocations #72656
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This removes ~30MB of LOH allocations when compiling Roslyn
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sharwell
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Mar 21, 2024
| @@ -942,28 +943,28 @@ protected virtual TextLineCollection GetLinesCore() | |||
| internal sealed class LineInfo : TextLineCollection | |||
| { | |||
| private readonly SourceText _text; | |||
| private readonly int[] _lineStarts; | |||
| private readonly SegmentedList<int> _lineStarts; | |||
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💡 This could likely be changed to an ImmutableSegmentedList<int> with minimal penalty. Note that there is not currently a way to create the builder for that with a specific capacity, but I'm already working on a change to add that.
sharwell
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Mar 21, 2024
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jaredpar
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|
@dotnet/roslyn-compiler PTAL |
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Did perfview generate the tables in the PR description? |
Yes this is from the GC Stats view. |
RikkiGibson
approved these changes
Mar 22, 2024
| } | ||
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| var lineStarts = ArrayBuilder<int>.GetInstance(); | ||
| lineStarts.Add(0); // there is always the first line | ||
| var lineStarts = new SegmentedList<int>() |
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nit: consider changing var to SegmentedList here and using a collection-expr
sharwell
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Mar 22, 2024
333fred
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Mar 22, 2024
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Profiling revealed that these collections are resulting in large LOH allocations in the compiler. Flipping to Segmented collections to avoid the LOH. In total these changes remove 200MB+ of allocations from the LOH heap.
This results in significant improvements to the GC when running the compiler